Identification of Rfp (TRIM27) as a novel regulator of AP-1 mediated transcription
Abstract
The activator protein-1 (AP-1) class of basic leucine zipper transcription factors plays key roles in cellular events such as cell proliferation, cell differentiation and apoptosis. AP-1 is composed of three protein sub-families: Jun protein family, Fos protein family and Batf protein family. AP-1 proteins form homodimers and/or heterodimers and preferentially recognize 12-O-tetradecanoyl-phorbol-13-acetate (TPA) response elements on DNA. While Fos-Jun heterodimers stimulate transcriptional activation, Batf-Jun heterodimers negatively regulate AP-1 driven transcription. To understand how Batf mediates negative regulation of AP-1 driven transcription, potential interaction partners of Batf were determined using a yeast two hybrid screen. Ret finger protein (Rfp) was identified as a novel interaction partner for Batf. To confirm the specificity of the interaction, experiments were performed to demonstrate that Batf and Rfp interact in vitroand in vivo. Interestingly, overexpression of Rfp relieves negative regulation on AP-1 mediated transcription by Batf. This inhibition of Batf function is partially mediated by decreasing the stability of Batf. Similar to full length Rfp, expression of individual domains of Rfp Ring-B box(RB), coiled coil (CC) or Rfp domain (RD) also relieved negative regulation of AP-1 activity by Batf. However, these three subdomains had different effects on Batf stability. All of the Rfp subdomains increased Batf activity and acted as dominant interfering mutants of full-length Rfp. Rfp also interacts with c-Fos, another member of AP-1 family, in vivo. In contrast to the results with Batf, Rfp inhibits the activity of c-Fos-c-Jun dimers on AP-1 DNA by suppressing their transactivation potential. Rfp does not change the stability of c-Fos, nor do Rfp sub-domains exert any effect on the transactivation potential of c-Fos. These results show that full-length Rfp functions as a general regulator of AP-1 activity by decreasing the stability of Batf and suppressing c-Fos-c-Jun activity on AP-1 DNA.
Degree
M.S.
Advisors
Taparowsky, Purdue University.
Subject Area
Biology|Biochemistry
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