Abstract 2064: Regulation of the VHL tumor suppressor protein in hypoxia and through the cell cycle

2011 ◽  
Author(s):  
James R. Gnarra ◽  
Julie Brown ◽  
Weijun Liu
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Tumor Suppressor Protein ◽  
Vhl Tumor Suppressor Protein

scholarly journals Differential Regulation of E2F1, DP1, and the E2F1/DP1 Complex by ARF

2002 ◽  
Vol 22 (24) ◽  
pp. 8398-8408 ◽  
Author(s):  
Abhishek Datta ◽  
Alo Nag ◽  
Pradip Raychaudhuri
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Tumor Suppression ◽  
Differential Regulation ◽  
S Phase ◽  
Tumor Suppressor Protein ◽  
Regulatory Pathways

ABSTRACT The tumor suppressor protein ARF inhibits MDM2 to activate and stabilize p53. Recent studies provided evidence for p53-independent tumor suppression functions of ARF. For example, it has been shown that ARF induces proteolysis of certain E2F species, including E2F1. In addition, ARF relocalizes E2F1 from the nucleoplasm to nucleolus and inhibits E2F1-activated transcription. Because DP1 is a functional partner of the E2F family of factors, we investigated whether DP1 is also regulated by ARF. Here we show that DP1 associates with ARF. Coexpression of ARF relocalizes DP1 from the cytoplasm to the nucleolus, suggesting that DP1 is also a target of the ARF regulatory pathways. Surprisingly, however, the E2F1/DP1 complex is refractory to ARF regulation. Coexpression of E2F1 and DP1 blocks ARF-induced relocalization of either subunit to the nucleolus. The E2F1/DP1 complex localizes in the nucleoplasm, whereas ARF is detected in the nucleolus, suggesting that ARF does not interact with the E2F1/DP1 complex. Moreover, we show that E2F1 is more stable in the presence of ARF when coexpressed with DP1. These results suggest that ARF differentially regulates the free and heterodimeric forms of E2F1 and DP1. DP1 is a constitutively expressed protein, whereas E2F1 is mainly expressed at the G1/S boundary of the cell cycle. Therefore, the E2F1/DP1 complex is abundant only between late G1 and early S phase. Our results on the differential regulation E2F1, DP1, and the E2F1/DP1 complex suggest the possibility that ARF regulates the function of these cell cycle factors by altering the dynamics of their heterodimerization during progression from G1 to S phase.

scholarly journals mdm-2 inhibits the G1 arrest and apoptosis functions of the p53 tumor suppressor protein.

1996 ◽  
Vol 16 (5) ◽  
pp. 2445-2452 ◽  
Author(s):  
J Chen ◽  
X Wu ◽  
J Lin ◽  
A J Levine
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Biological Activities ◽  
Tumor Suppressor Protein ◽  
G1 Arrest ◽  
Physical Interaction ◽  
P53 Tumor Suppressor ◽  
Cycle Arrest ◽  
P53 Tumor Suppressor Protein

The mdm-2 gene encodes a 90-kDa polypeptide that binds specifically to the p53 tumor suppressor protein. This physical interaction results in the inhibition of the transcriptional functions of p53 (J. Chen, J. Lin, and A. J. Levine, Mol. Med. 1:142-152, 1995, and J. Momand, G. P. Zambetti, D. C. Olson, D. George, and A. J. Levine, Cell 69:1237-1245, 1992). Experiments are described that demonstrate the ability of mdm-2 to abrogate both the p53-mediated cell cycle arrest and the apoptosis functions. In addition, the results presented here suggest that mdm-2 binding to p53 and the resultant inhibition of p53 transcription functions are critical for reversing p53-mediated cell cycle arrest. The N-terminal half or domain of the mdm-2 protein is sufficient to regulate these biological activities of p53, consistent with the possibility that the highly conserved central acidic region and the C-terminal putative zinc fingers of mdm-2 may encode other functions.

scholarly journals MyoD induced cell cycle arrest is associated with increased nuclear affinity of the Rb protein.

1993 ◽  
Vol 4 (7) ◽  
pp. 705-713 ◽  
Author(s):  
A M Thorburn ◽  
P A Walton ◽  
J R Feramisco
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Dna Synthesis ◽  
Cell Cycle Arrest ◽  
S Phase ◽  
Tumor Suppressor Protein ◽  
G1 Phase ◽  
Induced Expression ◽  
Rb Protein ◽  
Cycle Arrest

In studying the mechanism through which the myogenic determination protein MyoD prevents entry into the S phase of the cell cycle, we have found a relationship between MyoD and the retinoblastoma (Rb) tumor suppressor protein. By direct needle microinjection of purified recombinant MyoD protein into quiescent fibroblasts, which were then induced to proliferate by serum, we found that MyoD arrested progression of the cell cycle, in agreement with studies utilizing expression constructs for MyoD. By studying temporal changes in cells injected with MyoD protein, it was found that MyoD did not prevent serum induced expression of the protooncogene c-Fos, an event that occurs in the G0 to G1 transition of the cycle. Injection of the MyoD protein as late as 8 h after the addition of serum still caused an inhibition in DNA synthesis, suggesting that MyoD inhibits the G1 to S transition as opposed to the G0 to G1 transition. MyoD injection did not prevent the expression of cyclin A. However MyoD injection did result in a block in the increase in Rb extractibility normally seen in late G1 phase cells. As this phenomenon is associated with the hyperphosphorylation of Rb at this point in the cell cycle and is correlated with progression into S phase, this provides further evidence that MyoD blocks the cycle late in G1.

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