New Insights into Transcriptional Regulation by Rb.

The retinoblastoma (Rb) protein is a key regulator of cell proliferation, differentiation, and tumorigenesis. Initial studies of Rb revealed that it binds to, and decreases the activity of, the E2F family of transcription factors. Over the last decade, the mechanisms by which Rb regulates E2F activity have been well-studied. These investigations have lead to a commonly held belief that Rb functions solely as a transcriptional repressor. However, although not as commonly discussed, there are many examples of Rb synergizing with site-specific transcription factors to activate transcription. This Rb-mediated activation appears to be cell type-specific, transcription factor-specific, and even promoter-specific. This chapter details some of the examples of Rb-mediated transcriptional activation and suggests future studies that could provide insight into the mechanisms by which Rb can function to positively regulate transcription. [ABSTRACT FROM AUTHOR]