Bunched and Madm: a novel growth-regulatory complex?

Abstract Background Flavonoid biosynthesis in plants is primarily regulated at the transcriptional level by transcription factors modulating the expression of genes encoding enzymes in the flavonoid pathway. One of the most studied transcription factor complexes involved in this regulation consists of a MYB, bHLH and WD40. However, in Chinese Narcissus (Narcissus tazetta L. var. chinensis), a popular monocot bulb flower, the regulatory mechanism of flavonoid biosynthesis remains unclear. Results In this work, genes related to the regulatory complex, NtbHLH1 and a R2R3-MYB NtMYB6, were cloned from Chinese Narcissus. Phylogenetic analysis indicated that NtbHLH1 belongs to the JAF13 clade of bHLH IIIf subgroup, while NtMYB6 was highly homologous to positive regulators of proanthocyanidin biosynthesis. Both NtbHLH1 and NtMYB6 have highest expression levels in basal plates of Narcissus, where there is an accumulation of proanthocyanidin. Ectopic over expression of NtbHLH1 in tobacco resulted in an increase in anthocyanin accumulation in flowers, and an up-regulation of expression of the endogenous tobacco bHLH AN1 and flavonoid biosynthesis genes. In contrast, the expression level of LAR gene was significantly increased in NtMYB6-transgenic tobacco. Dual luciferase assays showed that co-infiltration of NtbHLH1 and NtMYB6 significantly activated the promoter of Chinese Narcissus DFR gene. Furthermore, a yeast two-hybrid assay confirmed that NtbHLH1 interacts with NtMYB6. Conclusions Our results suggest that NtbHLH1 may function as a regulatory partner by interacting directly with NtMYB6 to enhance proanthocyanidin accumulation in Chinese Narcissus.

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Regulation of the water channel aquaporin-1: isolation and reconstitution of the regulatory complex

Cell Biology International ◽

10.1016/j.cellbi.2003.11.003 ◽

2004 ◽

Vol 28 (1) ◽

pp. 7-17 ◽

Cited By ~ 50

Author(s):

R Abu-Hamdah

Keyword(s):

Water Channel ◽

Aquaporin 1 ◽

Regulatory Complex

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Differential roles of microtubule assembly and sliding in proplatelet formation by megakaryocytes

Blood ◽

10.1182/blood-2005-06-2204 ◽

2005 ◽

Vol 106 (13) ◽

pp. 4076-4085 ◽

Cited By ~ 142

Author(s):

Sunita R. Patel ◽

Jennifer L. Richardson ◽

Harald Schulze ◽

Eden Kahle ◽

Niels Galjart ◽

...

Keyword(s):

Fluorescent Protein ◽

Average Rate ◽

Blood Platelets ◽

Time Lapse ◽

Microtubule Assembly ◽

Alternative Mechanism ◽

Differentiated Cells ◽

Continuous Polymerization ◽

Regulatory Complex ◽

Green Fluorescent

Megakaryocytes are terminally differentiated cells that, in their final hours, convert their cytoplasm into long, branched proplatelets, which remodel into blood platelets. Proplatelets elongate at an average rate of 0.85 μm/min in a microtubule-dependent process. Addition of rhodamine-tubulin to permeabilized proplatelets, immunofluorescence microscopy of the microtubule plus-end marker end-binding protein 3 (EB3), and fluorescence time-lapse microscopy of EB3–green fluorescent protein (GFP)–expressing megakaryocytes reveal that microtubules, organized as bipolar arrays, continuously polymerize throughout the proplatelet. In immature megakaryocytes lacking proplatelets, microtubule plus-ends initiate and grow by centrosomal nucleation at rates of 8.9 to 12.3 μm/min. In contrast, plus-end growth rates of microtubules within proplatelets are highly variable (1.5-23.5 μm/min) and are both slower and faster than those seen in immature cells. Despite the continuous assembly of microtubules, proplatelets continue to elongate when net microtubule assembly is arrested. One alternative mechanism for force generation is microtubule sliding. Triton X-100–permeabilized proplatelets containing dynein and its regulatory complex, dynactin, but not kinesin, elongate with the addition of adenosine triphosphate (ATP) at a rate of 0.65 μm/min. Retroviral expression in megakaryocytes of dynamitin (p50), which disrupts dynactindynein function, inhibits proplatelet elongation. We conclude that while continuous polymerization of microtubules is necessary to support the enlarging proplatelet mass, the sliding of overlapping microtubules is a vital component of proplatelet elongation.

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The Ciliary Protein Cystin Forms a Regulatory Complex with Necdin to Modulate Myc Expression

PLoS ONE ◽

10.1371/journal.pone.0083062 ◽

2013 ◽

Vol 8 (12) ◽

pp. e83062 ◽

Cited By ~ 6

Author(s):

Maoqing Wu ◽

Chaozhe Yang ◽

Binli Tao ◽

Su Bu ◽

Lisa M. Guay-Woodford

Keyword(s):

Ciliary Protein ◽

Regulatory Complex

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Assembly of the Drosophila 26 S proteasome is accompanied by extensive subunit rearrangements

Biochemical Journal ◽

10.1042/bj20011520 ◽

2002 ◽

Vol 365 (2) ◽

pp. 527-536 ◽

Cited By ~ 26

Author(s):

Éva KURUCZ ◽

István ANDÓ ◽

Máté SÜMEGI ◽

Harald HÖLZL ◽

Barbara KAPELARI ◽

...

Keyword(s):

Monoclonal Antibodies ◽

26S Proteasome ◽

Cross Linking ◽

20S Proteasome ◽

Electron Microscopic ◽

Immunoblot Assay ◽

Optimal Conformation ◽

Regulatory Complex ◽

Atpase Subunits ◽

The Cross

The subunit contacts in the regulatory complex of the Drosophila 26 S proteasome were studied through the cross-linking of closely spaced subunits of the complex, and analysis of the cross-linking pattern in an immunoblot assay with the use of subunit-specific monoclonal antibodies. The cross-linking pattern of the purified 26 S proteasome exhibits significant differences as compared with that of the purified free regulatory complex. It is shown that the observed differences are due to extensive rearrangement of the subunit contacts accompanying the assembly of the 26 S proteasome from the regulatory complex and the 20S proteasome. Cross-linking studies and electron microscopic examinations revealed that these changes are reversible and follow the assembly or the disassembly of the 26 S proteasome. Although the majority of the changes observed in the subunit contacts affected the hexameric ring of the ATPase subunits, the alterations extended over the whole of the regulatory complex, affecting subunit contacts even in the lid subcomplex. Changes in the subunit contacts, similar to those in the regulatory complex, were detected in the 20S proteasome. These observations indicate that the assembly of the 26 S proteasome is not simply a passive docking of two rigid subcomplexes. In the course of the assembly, the interacting subcomplexes mutually rearrange their structures so as to create the optimal conformation required for the assembly and the proper functioning of the 26S proteasome.

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Control of mRNA turnover as a mechanism of glucose repression in Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.12.7.2941-2948.1992 ◽

1992 ◽

Vol 12 (7) ◽

pp. 2941-2948

Author(s):

A Lombardo ◽

G P Cereghino ◽

I E Scheffler

Keyword(s):

Saccharomyces Cerevisiae ◽

Succinate Dehydrogenase ◽

Half Life ◽

Glucose Repression ◽

Promoter Sequence ◽

Regulatory Elements ◽

Mrna Levels ◽

Protein Subunit ◽

Gene Encoding ◽

Regulatory Complex

We have examined the expression of the gene encoding the iron-protein subunit (Ip) of succinate dehydrogenase in Saccharomyces cerevisiae. The gene had been cloned by us and shown to be subject to glucose regulation (A. Lombardo, K. Carine, and I. E. Scheffler, J. Biol. Chem. 265:10419-10423, 1990). We discovered that a significant part of the regulation of the Ip mRNA levels by glucose involves the regulation of the turnover rate of this mRNA. In the presence of glucose, the half-life appears to be less than 5 min, while in glycerol medium, the half-life is greater than 60 min. The gene is also regulated transcriptionally by glucose. The upstream promoter sequence appeared to have four regulatory elements with consensus sequences shown to be responsible for the interaction with the HAP2/3/4 regulatory complex. A deletion analysis has shown that the two distal elements are redundant. These measurements were carried out by Northern (RNA) analyses of Ip mRNA transcripts as well as by assays of beta-galactosidase activity in cells carrying constructs of the Ip promoter linked to the lacZ coding sequence. These observations on the regulation of mRNA stability were also extended to the mRNA of the flavoprotein subunit of succinate dehydrogenase and in some experiments of iso-1-cytochrome c.

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