Proteasome activator PA28γ stimulates degradation of GSK3-phosphorylated insulin transcription activator MAFA

MAFA is a member of the MAF family of basic leucine zipper transcription factors and is a critical regulator of insulin gene expression and islet β-cell function. To be degraded by the proteasome, MAFA must be phosphorylated by GSK3 and MAP kinases at multiple serine and threonine residues (Ser49, Thr53, Thr57, Ser61, and Ser65) within its amino-terminal domain. In this study, we report that MAFA degradation is stimulated by PA28γ (REGγ and PSME3), a member of a family of proteasome activators that bind and activate the 20S proteasome. To date, only a few PA28γ-proteasome pathway substrates have been identified, including steroid receptor coactivator 3 (SRC3) and the cell cycle inhibitor p21 (CIP1). PA28γ binds to MAFA, induces its proteasomal degradation, and thereby attenuates MAFA-driven transcriptional activation of the insulin promoter. Co-expression of GSK3 enhanced the PA28γ-mediated degradation of MAFA, but mutants that contained alanine substitutions at the MAFA phosphorylation sites did not bind PA28γ and were resistant to degradation. We also found that a PA28γ mutant (N151Y) that did not stimulate p21 degradation enhanced MAFA degradation, and another mutant (K188D) that promoted greater p21 degradation did not enhance MAFA degradation. These results suggest that PA28γ stimulates MAFA degradation through a novel molecular mechanism that is distinct from that for the degradation of p21.

Download Full-text

Cap ‘n’ collar B cooperates with a small Maf subunit to specify pharyngeal development and suppress deformed homeotic function in the Drosophila head

Development ◽

10.1242/dev.127.18.4023 ◽

2000 ◽

Vol 127 (18) ◽

pp. 4023-4037 ◽

Cited By ~ 3

Author(s):

A. Veraksa ◽

N. McGinnis ◽

X. Li ◽

J. Mohler ◽

W. McGinnis

Keyword(s):

Transcriptional Activation ◽

Protein Function ◽

Leucine Zipper ◽

Suppressive Effect ◽

Basic Leucine Zipper ◽

Transcriptional Activation Domain ◽

Amino Terminal ◽

Culture Cells ◽

Mandibular Segment ◽

Direct Binding

The basic-leucine zipper protein Cap ‘n’ collar B (CncB) suppresses the segmental identity function of the Hox gene Deformed (Dfd) in the mandibular segment of Drosophila embryos. CncB is also required for proper development of intercalary, labral and mandibular structures. In this study, we provide evidence that the CncB-mediated suppression of Dfd requires the Drosophila homolog of the mammalian small Maf proteins, Maf-S, and that the suppression occurs even in the presence of high amounts of Dfd protein. Interestingly, the CncB/Maf-S suppressive effect can be partially reversed by overexpression of Homothorax (Hth), suggesting that Hth and Extradenticle proteins antagonize the effects of CncB/Maf-S on Dfd function in the mandibular segment. In embryos, multimers of simple CncB/Maf-S heterodimer sites are transcriptionally activated in response to CncB, and in tissue culture cells the amino-terminal domain of CncB acts as a strong transcriptional activation domain. There are no good matches to CncB/Maf binding consensus sites in the known elements that are activated in response to Dfd and repressed in a CncB-dependent fashion. This suggests that some of the suppressive effect of CncB/Maf-S proteins on Dfd protein function might be exerted indirectly, while some may be exerted by direct binding to as yet uncharacterized Dfd response elements. We also show that ectopic CncB is sufficient to transform ventral epidermis in the trunk into repetitive arrays of ventral pharynx. We compare the functions of CncB to those of its vertebrate and invertebrate homologs, p45 NF-E2, Nrf and Skn-1 proteins, and suggest that the pharynx selector function of CncB is highly conserved on some branches of the evolutionary tree.

Download Full-text

The proto-oncogene HLF and the related basic leucine zipper protein TEF display highly similar DNA-binding and transcriptional regulatory properties

Blood ◽

10.1182/blood.v87.11.4607.bloodjournal87114607 ◽

1996 ◽

Vol 87 (11) ◽

pp. 4607-4617 ◽

Cited By ~ 21

Author(s):

SP Hunger ◽

S Li ◽

MZ Fall ◽

L Naumovski ◽

ML Cleary

Keyword(s):

Amino Acid ◽

Dna Binding ◽

Transcriptional Activation ◽

Leucine Zipper ◽

Lymphoblastic Leukemia ◽

Consensus Sequence ◽

Basic Leucine Zipper ◽

Amino Terminal ◽

Transcriptional Regulatory ◽

Regulatory Properties

Genes encoding transcription factors are frequently altered by chromosomal translocations in acute lymphoblastic leukemia (ALL), suggesting that aberrant transcriptional regulation plays a prominent role in leukemogenesis. E2A-hepatic leukemia factor (HLF), a chimeric transcription factor created by the t(17;19), consists of the amino terminal portion of E2A proteins, including two experimentally defined transcriptional activation domains (TADs), fused to the HLF DNA binding and protein dimerization basic leucine zipper (bZIP) domain. To understand the mechanisms by which E2A-HLF induces leukemia and the crucial functions contributed by each constituent of the chimera, it is essential to define the normal transcriptional regulatory properties of HLF and related bZIP proteins. To address these questions, we cloned the human homologue of TEF/VBP, a bZIP protein closely related to HLF. Using a binding site selection assay, we found that TEF bound preferentially to the consensus sequence 5′-GTTACGTAAT-3′, which is identical to the previously determined HLF recognition site. TEF and HLF activated transcription of consensus site-containing reporter genes in several different cell types with similar potencies. Using GAL4 chimeric proteins, a TAD was mapped to a discrete approximate 40 amino acid region of TEF and HLF within which they share 72% amino acid identity and 85% similarity. The TEF/HLF activation domain (THAD) has a predicted helical secondary structure, but shares no sequence homology with previously reported TADs. The THAD contained most, if not all, of the transcriptional activation properties present in both TEF and HLF and its deletion completely abrogated transcriptional activity of TEF and HLF in both mammalian cells and yeast. Thus, TEF and HLF share indistinguishable DNA-binding and transcriptional regulatory properties, whose alteration in leukemia may be pathogenetically important.

Download Full-text

Regulation of the Amino-Terminal Transcription Activation Domain of Progesterone Receptor by a Cofactor-Induced Protein Folding Mechanism

Molecular and Cellular Biology ◽

10.1128/mcb.25.20.8792-8808.2005 ◽

2005 ◽

Vol 25 (20) ◽

pp. 8792-8808 ◽

Cited By ~ 30

Author(s):

Suzanne E. Wardell ◽

Stanley C. Kwok ◽

Lori Sherman ◽

Robert S. Hodges ◽

Dean P. Edwards

Keyword(s):

Progesterone Receptor ◽

Transcriptional Activation ◽

Transcriptional Activity ◽

Leucine Zipper ◽

Activation Domain ◽

Basic Leucine Zipper ◽

Transcriptional Activation Domain ◽

Amino Terminal ◽

Terminal Domain ◽

Helical Content

ABSTRACT We previously identified a small basic leucine zipper (bZIP) protein, Jun dimerization protein 2 (JDP-2), that acts as a coregulator of the N-terminal transcriptional activation domain of progesterone receptor (PR). We show here that JDP-2, through interaction with the DNA binding domain (DBD), induces or stabilizes structure in the N-terminal domain in a manner that correlates with JDP-2 stimulation of transcriptional activity. Circular dichroism spectroscopy experiments showed that JDP-2 interaction caused a significant increase in overall helical content of a two-domain PR polypeptide containing the N-terminal domain and DBD and that the change in structure resides primarily in the N-terminal domain. Thermal melt curves showed that the JDP-2/PR complex is significantly more stable than either protein alone, and partial proteolysis confirmed that JDP-2 interaction alters conformation of the N-terminal domain of PR. Functional analysis of N-terminal domain mutants and receptor chimeras provides evidence that the stimulatory effect of JDP-2 on transcriptional activity of PR is mediated through an interdomain communication between the DBD and the N-terminal domain and that transcriptional activity and functional response to JDP-2 are mediated by multiple elements of the N-terminal domain as opposed to a discrete region.

Download Full-text

Research Resource: The Pdx1 Cistrome of Pancreatic Islets

Molecular Endocrinology ◽

10.1210/me.2011-1231 ◽

2012 ◽

Vol 26 (3) ◽

pp. 521-533 ◽

Cited By ~ 37

Author(s):

Cynthia Khoo ◽

Juxiang Yang ◽

Samuel A. Weinrott ◽

Klaus H. Kaestner ◽

Ali Naji ◽

...

Keyword(s):

Pancreatic Islets ◽

Target Genes ◽

Cell Function ◽

Late Onset ◽

Endocrine System ◽

Insulin Promoter ◽

Chromatin Immunoprecipitation Sequencing ◽

Β Cell Function ◽

Mouse Islets ◽

Target Set

Abstract The homeodomain transcription factor pancreas duodenal homeobox 1 (Pdx1, also known as insulin promoter factor 1) is a master regulator of pancreas development, as mice or humans lacking Pdx1 function are a pancreatic. Importantly, heterozygous mutations in Pdx1 cause early and late onset forms of diabetes in humans. Despite these central roles in development and adult β-cell function, we have only rudimentary knowledge of the transcriptome targets of Pdx1 that mediate these phenotypes. Therefore, we performed global location analysis of Pdx1 occupancy in pancreatic islets. We used evolutionary conservation of target genes to identify the most relevant Pdx1 targets by performing chromatin immunoprecipitation sequencing on both human and mouse islets. Remarkably, the conserved target set is highly enriched for genes annotated to function in endocrine system and metabolic disorders, various signaling pathways, and cell survival, providing a molecular explanation for many of the phenotypes resulting from Pdx1 deficiency.

Download Full-text

A feedback transcriptional mechanism controls the level of the arginine/lysine transporter cat-1 during amino acid starvation

Biochemical Journal ◽

10.1042/bj20060941 ◽

2007 ◽

Vol 402 (1) ◽

pp. 163-173 ◽

Cited By ~ 64

Author(s):

Alex B. Lopez ◽

Chuanping Wang ◽

Charlie C. Huang ◽

Ibrahim Yaman ◽

Yi Li ◽

...

Keyword(s):

Amino Acid ◽

Transcriptional Activation ◽

Transcriptional Repression ◽

Mammalian Cells ◽

Leucine Zipper ◽

Amino Acid Starvation ◽

Translation Initiation Factor ◽

Initiation Factor ◽

Basic Leucine Zipper

The adaptive response to amino acid limitation in mammalian cells inhibits global protein synthesis and promotes the expression of proteins that protect cells from stress. The arginine/lysine transporter, cat-1, is induced during amino acid starvation by transcriptional and post-transcriptional mechanisms. It is shown in the present study that the transient induction of cat-1 transcription is regulated by the stress response pathway that involves phosphorylation of the translation initiation factor, eIF2 (eukaryotic initiation factor-2). This phosphorylation induces expression of the bZIP (basic leucine zipper protein) transcription factors C/EBP (CCAAT/enhancer-binding protein)-β and ATF (activating transcription factor) 4, which in turn induces ATF3. Transfection experiments in control and mutant cells, and chromatin immunoprecipitations showed that ATF4 activates, whereas ATF3 represses cat-1 transcription, via an AARE (amino acid response element), TGATGAAAC, in the first exon of the cat-1 gene, which functions both in the endogenous and in a heterologous promoter. ATF4 and C/EBPβ activated transcription when expressed in transfected cells and they bound as heterodimers to the AARE in vitro. The induction of transcription by ATF4 was inhibited by ATF3, which also bound to the AARE as a heterodimer with C/EBPβ. These results suggest that the transient increase in cat-1 transcription is due to transcriptional activation caused by ATF4 followed by transcriptional repression by ATF3 via a feedback mechanism.

Download Full-text

Arabidopsis bZIP11 is a susceptibility factor during Pseudomonas syringae infection

10.1101/2020.11.25.398727 ◽

2020 ◽

Author(s):

Matthew J. Prior ◽

Jebasingh Selvanayagam ◽

Jung-Gun Kim ◽

Monika Tomar ◽

Martin Jonikas ◽

...

Keyword(s):

Transcription Factor ◽

Pseudomonas Syringae ◽

Leucine Zipper ◽

Host Cells ◽

Amino Acid Transporters ◽

Secretion Systems ◽

Transcription Activator ◽

Tal Effectors ◽

Basic Leucine Zipper ◽

Transcription Networks

AbstractThe induction of plant nutrient secretion systems is critical for successful pathogen infection. Some bacterial pathogens, e.g. Xanthomonas species, use TAL (transcription activator-like) effectors to induce transcription of SWEET sucrose efflux transporters. Pseudomonas syringae pathovar (pv.) tomato strain DC3000 lacks TAL effectors, yet is able to induce multiple SWEETs in Arabidopsis thaliana by unknown mechanisms. Since bacteria require other nutrients besides sugars for efficient reproduction, we hypothesized that Pseudomonas may depend on host transcription factors involved in secretory programs to increase access to essential nutrients. Bioinformatic analyses identified the Arabidopsis basic-leucine zipper transcription factor bZIP11 as a potential regulator of nutrient transporters, including SWEETs and UmamiT amino acid transporters. Inducible downregulation of bZIP11 expression in Arabidopsis resulted in reduced growth of P. syringae pv. tomato strain DC3000, whereas inducible overexpression of bZIP11 resulted in increased bacterial growth, supporting the hypothesis that bZIP11 regulated transcription programs are essential for maximal pathogen titer in leaves. Our data are consistent with a model in which a pathogen alters host transcription factor expression upstream of secretory transcription networks to promote nutrient efflux from host cells.

Download Full-text

Interactions among LRF-1, JunB, c-Jun, and c-Fos define a regulatory program in the G1 phase of liver regeneration

Molecular and Cellular Biology ◽

10.1128/mcb.12.10.4654-4665.1992 ◽

1992 ◽

Vol 12 (10) ◽

pp. 4654-4665

Author(s):

J C Hsu ◽

R Bravo ◽

R Taub

Keyword(s):

Cyclic Amp ◽

Transcriptional Activation ◽

Leucine Zipper ◽

G1 Phase ◽

Basic Leucine Zipper ◽

Relative Level ◽

Response Element ◽

Complex Interactions ◽

Cyclic Amp Response Element ◽

The Many

In regenerating liver, a physiologically normal model of cell growth, LRF-1, JunB, c-Jun, and c-Fos among Jun/Fos/LRF-1 family members are induced posthepatectomy. In liver cells, high levels of c-Fos/c-Jun, c-Fos/JunB, LRF-1/c-Jun, and LRF-1/JunB complexes are present for several hours after the G0/G1 transition, and the relative level of LRF-1/JunB complexes increases during G1. We provide evidence for dramatic differences in promoter-specific activation by LRF-1- and c-Fos-containing complexes. LRF-1 in combination with either Jun protein strongly activates a cyclic AMP response element-containing promoter which c-Fos/Jun does not activate. LRF-1/c-Jun, c-Fos/c-Jun, and c-Fos/JunB activate specific AP-1 and ATF site-containing promoters, and in contrast, LRF-1/JunB potently represses c-Fos- and c-Jun-mediated activation of these promoters. Repression is dependent on a region in LRF-1 that includes amino acids 40 to 84 (domain R) and the basic/leucine zipper domain. As the relative level of LRF-1/JunB complexes increases posthepatectomy, c-Fos/Jun-mediated ATF and AP-1 site activation is likely to decrease with simultaneous transcriptional activation of the many liver-specific genes whose promoters contain cyclic AMP response element sites. Thus, through complex interactions among LRF-1, JunB, c-Jun, and c-Fos, control of delayed gene expression may be established for extended times during the G1 phase of hepatic growth.

Download Full-text

CEBPA Mutations in 4708 Patients with Acute Myeloid Leukemia - Differential Impact of bZIP and TAD Mutations on Outcome

Blood ◽

10.1182/blood.2020009680 ◽

2021 ◽

Author(s):

Franziska Taube ◽

Julia Annabell Georgi ◽

Michael Kramer ◽

Sebastian Stasik ◽

Jan Moritz Middeke ◽

...

Keyword(s):

Leucine Zipper ◽

Prognostic Impact ◽

Basic Leucine Zipper ◽

Amino Terminal ◽

Transactivation Domains ◽

Molecular Features ◽

Cebpa Mutations ◽

Biallelic Mutations ◽

Carboxy Terminal

Biallelic mutations of the CEBPA gene (CEBPAbi) define a distinct entity associated with favorable prognosis, however the role of monoallelic mutations (CEBPAsm) is poorly understood. We retrospectively analyzed 4708 adult AML patients recruited into Study Alliance Leukemia trials to investigate the prognostic impact of CEBPAsm. CEBPA mutations were identified in 240 patients (5.1%), 131 CEBPAbi and 109 CEBPAsm (60 affecting the amino-terminal transactivation domains (CEBPAsmTAD) and 49 the carboxy-terminal DNA-binding or basic leucine zipper region (CEBPAsmbZIP)). Interestingly, CEBPAbi and CEBPAsmbZIP patients shared several clinical factors, i.e. were significantly younger (median 46 years and 50 years) and had higher WBC counts at diagnosis (median 23.7 and 35.7 109/l) compared to CEBPAsmTAD patients (median age 63 yrs., median WBC 13.1 109/l; p<.001). Co-mutations were also similar in both groups, e.g. GATA2 mutations (35.1% CEBPAbi; 36.7% CEBPAsmbZIP vs. 6.7% CEBPAsmTAD; p<.001) or NPM1 mutations (3.1% CEBPAbi; 8.2% CEBPAsmbZIP vs. 38.3% CEBPAsmTAD; p<.001). CEBPAbi and CEBPAsmbZIP, but not CEBPAsmTAD were associated with significantly improved overall (median OS: 103 and 63 vs. 13 months) and event-free survival (median EFS: 20.7 and 17.1 vs. 5.7 months), in univariate and multivariable analyses. More detailed analysis revealed that the clinical and molecular features as well as the favorable survival were confined to patients showing in-frame mutations in bZIP (CEBPAbZIP-inf). When grouping patients into CEBPAbZIP-inf and CEBPAother (including CEBPAsmTAD and other non-CEBPAbZIP-inf patients), only CEBPAbZIP-inf patients showed superior CR rates and the longest median OS and EFS, arguing for a previously undefined prognostic role of this type of mutations.

Download Full-text

Jun dimerization protein 2 is a critical component of the Nrf2/MafK complex regulating the response to ROS homeostasis

Cell Death and Disease ◽

10.1038/cddis.2013.448 ◽

2013 ◽

Vol 4 (11) ◽

pp. e921-e921 ◽

Cited By ~ 34

Author(s):

S Tanigawa ◽

C H Lee ◽

C S Lin ◽

C C Ku ◽

H Hasegawa ◽

...

Keyword(s):

Oxidative Stress ◽

Transcriptional Activation ◽

Leucine Zipper ◽

Target Genes ◽

Critical Role ◽

Notch Receptor ◽

Heme Oxygenase 1 ◽

Related Factor ◽

Mobility Shift ◽

Basic Leucine Zipper

Abstract Oxidative stress and reactive oxygen species (ROS) are associated with diseases such as cancer, cardiovascular complications, inflammation and neurodegeneration. Cellular defense systems must work constantly to control ROS levels and to prevent their accumulation. We report here that the Jun dimerization protein 2 (JDP2) has a critical role as a cofactor for transcription factors nuclear factor-erythroid 2-related factor 2 (Nrf2) and small Maf protein family K (MafK) in the regulation of the antioxidant-responsive element (ARE) and production of ROS. Chromatin immunoprecipitation–quantitative PCR (qPCR), electrophoresis mobility shift and ARE-driven reporter assays were carried out to examine the role of JDP2 in ROS production. JDP2 bound directly to the ARE core sequence, associated with Nrf2 and MafK (Nrf2–MafK) via basic leucine zipper domains, and increased DNA-binding activity of the Nrf2–MafK complex to the ARE and the transcription of ARE-dependent genes. In mouse embryonic fibroblasts from Jdp2-knockout (Jdp2 KO) mice, the coordinate transcriptional activation of several ARE-containing genes and the ability of Nrf2 to activate expression of target genes were impaired. Moreover, intracellular accumulation of ROS and increased thickness of the epidermis were detected in Jdp2 KO mice in response to oxidative stress-inducing reagents. These data suggest that JDP2 is required to protect against intracellular oxidation, ROS activation and DNA oxidation. qPCR demonstrated that several Nrf2 target genes such as heme oxygenase-1, glutamate–cysteine ligase catalytic and modifier subunits, the notch receptor ligand jagged 1 and NAD(P)H dehydrogenase quinone 1 are also dependent on JDP2 for full expression. Taken together, these results suggest that JDP2 is an integral component of the Nrf2–MafK complex and that it modulates antioxidant and detoxification programs by acting via the ARE.

Download Full-text