Analysis of the Mechanism of Action of RPF1: Potentiator of Progesterone Receptor and p53-dependent Transcriptional Activity
Abstract
HRPF1/Nedd4 was originally identified in our laboratory as a potentiator of progesterone-receptor transcriptional activity, and subsequently demonstrated to similarly modulate p53-dependent transcription. As a hect' E3 ubiquitin ligase, hRPFl/Nedd4's domain structure suggests that it is able to target substrate proteins for ubiquitination. We have been interested in identifying nuclear substrates of hRPF1/Nedd4's ubiquitination activity with a view to understanding the mechanism by which hRPFl/Nedd4 is able to modulate such transcriptional events. We present compelling evidence that hPRTB, a novel proline-rich protein which colocalizes with splicing machinery in nuclear speckles, is a bona fide' nuclear substrate of the WW hect E3 ubiquitin ligase, hRPFl/Nedd4. In addition to providing the first description of a nuclear substrate of mammalian Nedd4, these observations underscore the potential for regulation of splicing proteins by the ubiquitination. Lastly, with the identification of a leucine-rich rev-like nuclear export sequence within hRPFI/Nedd4, we propose that nuclear import/export is an important component of the regulation between the primarily cytoplasmic E3 enzyme, hRPFl/Nedd4 and its nuclear substrate, hPRTB. Thus, we have firmly established a role for hRPFl/Nedd4 within the nucleus, and identified a substrate protein which may explain in part our observed effects upon activated transcription.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 2000
- Accession Number
- ADB266028
Entities
People
- D. Mcdonnell
- Maria Huacani
Organizations
- Duke University Hospital