Cyclin D1 Associates with the TBP-associated factor TAFII250 to regulate Sp1-mediated transcription

Abstract

We have previously shown that Sp1-mediated transcription is stimulated by Rb and repressed by cyclin D1. The stimulation of Sp1 transcriptional activity by Rb is conferred, in part, through a direct interaction with the TBP-associated factor TAF II 250. Here we investigated the mechanism(s) through which cyclin D1 represses Sp1. We examined the ability of cyclin D1 to regulate transcription mediated by Gal4-Sp1 fusion proteins, which contain the Gal4 DNA-binding domain and Sp1 trans-activation domain(s). The domain of Sp1 su cient to confer repression by cyclin D1 was mapped to a region important for interaction with TAF II 110. We further demonstrate that TAF II 250-cyclin D1 complexes can be immunoprecipitated from mammalian and baculovirus-infected insect cells and that recombinant GST-TAF II 250 (amino acids 1 ± 434) associates with cyclin D1 in vitro. Moreover, the overexpression of Rb or CDK4 reduced the level of TAF II 250-cyclin D1 complex. The amino terminus of cyclin D1 (amino acids 1 ± 100) was su cient for association with TAF II 250 and for repressing Sp1-mediated transcription. Taken together, the results suggest that cyclin D1 may regulate transcription by interacting directly or indirectly with TAF II 250.

Glucosamine activates the plasminogen activator inhibitor 1 gene promoter through Sp1 DNA binding sites in glomerular mesangial cells.

“…Thus, glucosamine may also have augmented transcriptional activation by Sp1 or affected interactions between Sp1 and other proteins. There are 4 transcriptional activation domains in Sp1 that interact with transcriptional cofactors, including subunits of the TF II D and CRSP complexes (70)(71)(72)(73). Recognized interactions between Sp1 and Smads (74), AP-1 (78), retinoblastoma protein (60,76), cyclin D (70), CBP/p300 (through progesterone receptors) (77), or other Sp1 molecules to form higher-order multimers (71) could all have been affected by glucosamine and merit further investigation.…”

Cyclin D1 suppresses retinoblastoma protein-mediated inhibition of TAFII250 kinase activity

“…Such a model would be supported by the possibility that Rb and cyclin D1 may bind to overlapping sites at the N-terminus of TAF II 250 (Figure 1). It has been previously reported that in co-infection assays, an increasing dose of an Rb-expressing baculovirus, co-infected with baculoviruses expressing TAF II 250 and cyclin D1, could apparently reduce the amount of cyclin D1 and TAF II 250 found complexed following immunoprecipitation (Adnane et al, 1999). This result suggested that Rb was competing with cyclin D1 for binding to TAF II 250.…”

“…It has also been demonstrated that cyclin D1 is able to bind to the amino terminus of hTAF II 250 (Adnane et al, 1999), though these latter studies were performed primarily through co-transfection assays and not with puri®ed proteins. We examined the Rb-and TAF II 250-binding properties of puri®ed cyclin D1 in vitro, using a baculovirus-expressed, GST-tagged, murine cyclin D1 protein.…”

“…Particularly interesting is the ®nding that, independent of cdks, D-type cyclins inhibit S phase-regulatory gene expression and cell cycle arrest mediated by DMP1, a novel transcription factor (Inoue and Sherr, 1998). Moreover, it has recently been shown that cyclin D1 is able to associate with the TAF II 250 subunit of the basal transcription factor TFIID (Adnane et al, 1999). In this study we have further characterized the interaction between cyclin D1 and TAF II 250, and have demonstrated a functional consequence of this interaction.…”

“…We have also recently shown that cyclin D1 is able to associate with TAF II 250 (Adnane et al, 1999). The D-type cyclins, together with cyclin-dependent kinases, are known to regulate transcription by inactivating Rb through phosphorylation (reviewed in Hunter and Pines, 1994).…”