The Retinoblastoma Protein Region Required for Interaction with the E2F Transcription Factor Includes the T/E1A Binding and Carboxy-Terminal Sequences

Huang, Shi; Shin, E K; Sheppard, Kelly-Ann; Chokroverty, Linda; Shan, Bei; Qian, Yue‐Wei; Lee, Eva Y.-H.P.; Yee, Amy S.

doi:10.1089/dna.1992.11.539

Cited by 37 publications

(25 citation statements)

References 36 publications

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“…Competitor wt consists of identical E2F sequences from the E2 promoter. Competitor A consists of a C-to-A mutation in each E2F site, and this mutant site exhibits reduced E2F binding (35). A typical E2F EMSA utilized 3 to 5 g of muscle cell extract and 0.1 ng of 32 P-labelled E2F probe.…”

Section: Methodsmentioning

confidence: 99%

“…In the case of RB, this pocket region is the site of tumorigenic inactivating mutations and is critical for the growth suppression function of RB. We and others have demonstrated that E2F binds to this region, providing a genetic correlation between E2F binding and growth suppression (1,3,8,9,32,35,56,57; for additional reviews, see references 28, 44, and 53). Different E2F complexes with RB or p107 are found during the G 1 and S phases of the cell cycle.…”

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confidence: 90%

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Multiple Changes in E2F Function and Regulation Occur upon Muscle Differentiation

Shin

Paulding

et al. 1995

Molecular and Cellular Biology

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We have examined regulation of the E2F transcription factor during differentiation of muscle cells. E2F regulates many genes involved in growth control and is also the target of regulation by diverse cellular signals, including the RB family of growth suppressors (e.g., the retinoblastoma protein [RB], p107, and p130). The following aspects of E2F function and regulation during muscle differentiation were investigated: (i) proteinprotein interactions, (ii) protein levels, (iii) phosphorylation of the E2F protein, and (iv) transcriptional activity. A distinct E2F complex was present in differentiated cells but not in undifferentiated cells. The p130 protein was a prominent component of the E2F complex associated with differentiation. In contrast, in undifferentiated cells, the p107 protein was the prominent component in one of three E2F complexes. In addition, use of a differentiation-defective muscle line provided genetic and biochemical evidence that quiescence and differentiation are separable events. Exclusive formation of the E2F-p130 complex did not occur in this differentiation-defective line; however, E2F complexes diagnostic of quiescence were readily apparent. Thus, sole formation of the E2F-p130 complex is a necessary event in terminal differentiation. Other changes in E2F function and regulation upon differentiation include decreased phosphorylation and increased repression by E2F. These observations suggest that the regulation of E2F function during terminal differentiation may proceed through differential interaction within the RB family and/or phosphorylation.In many cells, the trigger event in differentiation is withdrawal from the cell cycle with subsequent distinct morphological transitions. Muscle cells are an excellent system for examining molecular mechanisms of differentiation because they exhibit both permanent cell cycle withdrawal and a distinctive phenotype. Differentiation involves a transition from myoblasts to myotubes. Myoblasts are undifferentiated cells and are characterized by rapidly growing, mononucleated cells. In contrast, differentiated cells, or myotubes, are multinucleated and tubular. Upon differentiation, myotubes also express several muscle-specific markers. Because differentiated muscle cells (myotubes) are permanently withdrawn from the cell cycle, cellular mechanisms for the initiation and maintenance of the differentiated state must also exist (5).Studies with viral oncogenes have indicated a critical role for the retinoblastoma family of growth suppressors (the retinoblastoma protein [RB], p107, and p130) in the differentiation pathway. The expression of E1A and polyomavirus large T antigen may block muscle differentiation (7,49,66). It is well established that these two divergent viral oncogenes can bind the RB family (69). Importantly, when the binding site for RB family members was mutated, both E1A and polyomavirus large T antigen mutants no longer blocked differentiation (7, 49). These studies suggest that RB family members function in the control of differenti...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 90%

Multiple Changes in E2F Function and Regulation Occur upon Muscle Differentiation

Shin

Paulding

et al. 1995

Molecular and Cellular Biology

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“…Seven of these sites are contained within a 50 amino acid stretch within the C-terminal domain of the protein. This domain is sucient for c-Abl binding (Welch and Wang, 1993) and is required for association with many non-LXCXE containing pRb-associated proteins like E2F-1 (Huang et al, 1992;Qin et al, 1992). Two sites are located in the spacer region between the A and B domains.…”

Section: Rb Glutamic Acid Substitution Mutantsmentioning

confidence: 99%

Glutamic acid mutagenesis of retinoblastoma protein phosphorylation sites has diverse effects on function

2000

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The retinoblastoma tumor suppressor gene (Rb) has many functions within the cell including regulation of transcription, dierentiation, apoptosis, and the cell cycle. Regulation of these functions is mediated by phosphorylation at as many as 16 cyclin-dependent kinase (CDK) phosphorylation sites in vivo. The contribution of these sites to the regulation of the various Rb functions is not well understood. To characterize the eect of phosphorylation at these sites, we systematically mutagenized the serines or threonines to glutamic acid. Thirty-®ve mutants with dierent combinations of modi®ed phosphorylation sites were assayed for their ability to arrest the cell cycle and for their potential to induce dierentiation. Only the most highly substituted mutants failed to arrest cell cycle progression. However, mutants with as few as four modi®ed phosphorylation sites were unable to promote dierentiation. Other mutants had increased activity in this assay. We conclude that modi®cation of Rb phosphorylation sites can increase or decrease protein activity, that dierent Rb functions can be regulated independently by distinct combinations of sites, and that the eects of modi®cation at any one site are context dependent.

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“…A truncated RB1 composed of the A/B pocket and the C-terminus, which now includes the E2F-binding region (Huang et al, 1992), is able to act as a functional domain in the absence of the N-terminal region. Overexpression of the full length pRb in Saos-2 cells arrested these cells in G 1 and produced a large, at cell morphology.…”

Section: Introductionmentioning

confidence: 99%

Induction of apoptosis in Mv1Lu cells by expression of competitive RB1 mutants

Whitaker

Hansen

1997

Oncogene

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The Retinoblastoma Protein Region Required for Interaction with the E2F Transcription Factor Includes the T/E1A Binding and Carboxy-Terminal Sequences

Cited by 37 publications

References 36 publications

Multiple Changes in E2F Function and Regulation Occur upon Muscle Differentiation

Multiple Changes in E2F Function and Regulation Occur upon Muscle Differentiation

Glutamic acid mutagenesis of retinoblastoma protein phosphorylation sites has diverse effects on function

Induction of apoptosis in Mv1Lu cells by expression of competitive RB1 mutants

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