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

1992 ◽  
Vol 12 (10) ◽  
pp. 4654-4665
Author(s):  
J C Hsu ◽  
R Bravo ◽  
R Taub

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.

1992 ◽  
Vol 12 (10) ◽  
pp. 4654-4665 ◽  
Author(s):  
J C Hsu ◽  
R Bravo ◽  
R Taub

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.


2003 ◽  
Vol 23 (12) ◽  
pp. 4066-4082 ◽  
Author(s):  
Yongchang Chen ◽  
Shunhui Zhuang ◽  
Stijn Cassenaer ◽  
Darren E. Casteel ◽  
Tanima Gudi ◽  
...  

ABSTRACT Calcium induces transcriptional activation of the fos promoter by activation of the cyclic AMP response element (CRE)-binding protein (CREB), and in some cells its effect is enhanced synergistically by cyclic GMP (cGMP) through an unknown mechanism. We observed calcium-cGMP synergism in neuronal and osteogenic cells which express type II cGMP-dependent protein kinase (G-kinase); the effect on the fos promoter was mediated by the CRE and proportional to G-kinase activity. Dominant negative transcription factors showed involvement of CREB- and C/EBP-related proteins but not of AP-1. Expression of C/EBP-β but not C/EBP-α or -δ enhanced the effects of calcium and cGMP on a CRE-dependent reporter gene. The transactivation potential of full-length CREB fused to the DNA-binding domain of Gal4 was increased synergistically by calcium and cGMP, and overexpression of C/EBP-β enhanced the effect, while a dominant negative C/EBP inhibited it. With a mammalian two-hybrid system, coimmunoprecipitation experiments, and in vitro binding studies, we demonstrated that C/EBP-β and CREB interacted directly; this interaction involved the C terminus of C/EBP-β but occurred independently of CREB's leucine zipper domain. CREB Ser133 phosphorylation was stimulated by calcium but not by cGMP; in cGMP-treated cells, 32PO4 incorporation into C/EBP-β was decreased and C/EBP-β/CRE complexes were increased, suggesting regulation of C/EBP-β functions by G-kinase-dependent dephosphorylation. C/EBP-β and CREB associated with the fos promoter in intact cells, and the amount of promoter-associated C/EBP-β was increased by calcium and cGMP. We conclude that calcium and cGMP transcriptional synergism requires cooperation of CREB and C/EBP-β, with calcium and cGMP modulating the phosphorylation states of CREB and C/EBP-β, respectively.


1990 ◽  
Vol 10 (4) ◽  
pp. 1347-1357
Author(s):  
C J Kara ◽  
H C Liou ◽  
L B Ivashkiv ◽  
L H Glimcher

The cyclic AMP response element (CRE) is found in many cellular genes regulated by cyclic AMP, and similar elements are present in the early genes of adenovirus that are activated by E1A. The transcription factor CREB has previously been shown to bind this site, and cDNAs for CREB have recently been characterized. We report here the isolation of a cDNA encoding a human DNA-binding protein that also recognizes this motif in cellular and viral promoters. This protein, HB16, displays structural similarity to CREB and to c-Jun and c-Fos, which bind the related 12-O-tetradecanoylphorbol-13-acetate response element (TRE). HB16 contains a highly basic, putative DNA-binding domain and a leucine zipper structure thought to be involved in dimerization. Deletional analysis of HB16 demonstrated that the leucine zipper is required for its interaction with DNA. In addition, HB16 could form a complex with c-Jun but not with c-Fos. Despite its structural similarity to c-Jun and c-Fos and its interaction with c-Jun, HB16 had approximately a 10-fold-lower affinity for the TRE sequence than for the CRE sequence. Although HB16 and CREB both recognized the CRE motif, an extensive binding analysis of HB16 revealed differences in the fine specificity of binding of the two proteins. HB16 mRNA was found at various levels in many human tissues but was most abundant in brain, where its expression was widespread. The existence of more than one CRE-binding protein suggests that the CRE motif could serve multiple regulatory functions.


1990 ◽  
Vol 10 (4) ◽  
pp. 1347-1357 ◽  
Author(s):  
C J Kara ◽  
H C Liou ◽  
L B Ivashkiv ◽  
L H Glimcher

The cyclic AMP response element (CRE) is found in many cellular genes regulated by cyclic AMP, and similar elements are present in the early genes of adenovirus that are activated by E1A. The transcription factor CREB has previously been shown to bind this site, and cDNAs for CREB have recently been characterized. We report here the isolation of a cDNA encoding a human DNA-binding protein that also recognizes this motif in cellular and viral promoters. This protein, HB16, displays structural similarity to CREB and to c-Jun and c-Fos, which bind the related 12-O-tetradecanoylphorbol-13-acetate response element (TRE). HB16 contains a highly basic, putative DNA-binding domain and a leucine zipper structure thought to be involved in dimerization. Deletional analysis of HB16 demonstrated that the leucine zipper is required for its interaction with DNA. In addition, HB16 could form a complex with c-Jun but not with c-Fos. Despite its structural similarity to c-Jun and c-Fos and its interaction with c-Jun, HB16 had approximately a 10-fold-lower affinity for the TRE sequence than for the CRE sequence. Although HB16 and CREB both recognized the CRE motif, an extensive binding analysis of HB16 revealed differences in the fine specificity of binding of the two proteins. HB16 mRNA was found at various levels in many human tissues but was most abundant in brain, where its expression was widespread. The existence of more than one CRE-binding protein suggests that the CRE motif could serve multiple regulatory functions.


1994 ◽  
Vol 11 (4) ◽  
pp. 204-214 ◽  
Author(s):  
Marcin Banbura ◽  
Cathleen Ackland-Berglund ◽  
Soong-Ho Lee ◽  
Deborah Hamernik ◽  
Clinton Jones

1989 ◽  
Vol 8 (7) ◽  
pp. 2023-2028 ◽  
Author(s):  
T. Maekawa ◽  
H. Sakura ◽  
C. Kanei-Ishii ◽  
T. Sudo ◽  
T. Yoshimura ◽  
...  

1995 ◽  
Vol 312 (1) ◽  
pp. 17-21 ◽  
Author(s):  
R M O'Brien ◽  
N Halmi ◽  
P E Stromstedt ◽  
R L Printz ◽  
D K Granner

In response to specific extracellular signals, intracellular cyclic AMP levels increase, leading to a variety of responses including the alteration of transcription of many eukaryotic genes. This transcriptional effect is frequently mediated through the cyclic AMP-response element (CRE) motif T(T/G)ACGTCA. Using an expression screening approach we have cloned a yeast gene, MSN2, that encodes a 78 kDa protein that recognizes this consensus CRE motif. Phosphorylation of the MSN2 protein by the catalytic subunit of protein kinase A stimulates DNA binding in vitro. Two putative Cys2His2-type zinc fingers present in the C-terminal 79 amino acids of the MSN2 protein are sufficient to confer CRE-binding specificity. Therefore, MSN2 represents a novel CRE-binding protein distinct from the multiple previously characterized basic region-leucine zipper repeat CRE-binding proteins.


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