14 research outputs found
Multiple mRNA isoforms of the transcription activator protein CREB
We have characterized cDNA clones representing mouse
CREB (cyclic AMP responsive element binding protein)
mRNA isoforms. These include CREBA and CREBa, of
which the rat and human homologues have been
previously identified. Both encode proteins with CREbinding
activity and identical transactivation potential.
The additional CREB mRNA isoforms potentially encode
CREB related proteins. From the structural organization
of the mouse CREB gene we conclude that the multiple
transcripts are generated by alternative splicing. Furthermore
we show that specific CREB mRNA isoforms are
expressed at a high level in the adult testis. Expression
of these isoforms is induced after commencement of
spermatogenesis. In situ hybridization suggests that this
expression occurs predominantly in the primary spermatocytes.
Comparison of the CREB gene with the recently
isolated CREM (cAMP responsive element modulator)
cDNAs illustrates that the two genes have arisen by gene
duplication and have diverged to encode transcriptional
activators and repressors of the cAMP signal transduction
pathway
Multiple regions of TBP participate in the response to transcriptional activators in vivo
We used mutant yeast and human TBP molecules with an altered DNA-binding specificity to examine the role of TBP in transcriptional activation in vivo. We show that yeast TBP is functionally equivalent to human TBP for response to numerous transcriptional activators in human cells, including those that do not function in yeast. Despite the extensive conservation of TBP, its ability to respond to transcriptional activators in vivo is curiously resistant to clustered sets of alanine substitution mutations in different regions of the protein, including those that disrupt DNA binding and basal transcription in vitro. Combined sets of these mutations, however, can attenuate the in vivo activity of TBP and can differentially affect response to different activation domains. Although the activity of TBP mutants in vivo did not correlate with DNA binding or basal transcription in vitro, it did correlate with binding in vitro to the largest subunit of TFIID, hTAFII250. Together, these data suggest that TBP utilizes multiple interactions across its surface to respond to RNA polymerase II transcriptional activators in vivo; some of these interactions appear to involve recruitment of TBP into TFIID, whereas others are involved in response to specific types of transcriptional activators
TAFII250 Is a Bipartite Protein Kinase That Phosphorylates the Basal Transcription Factor RAP74
AbstractSome TAF subunits of transcription factor TFIID play a pivotal role in transcriptional activation by mediating protein–protein interactions, whereas other TAFs direct promoter selectivity via protein–DNA recognition. Here, we report that purified recombinant TAFII250 is a protein serine kinase that selectively phosphorylates RAP74 but not other basal transcription factors or common phosphoacceptor proteins. The phosphorylation of RAP74 also occurs in the context of the complete TFIID complex. Deletion analysis revealed that TAFII250 contains two distinct kinase domains each capable of autophosphorylation. However, both the N- and C-terminal kinase domains of TAFII250 are required for efficient transphosphorylation of RAP74 on serine residues. These findings suggest that the targeted phosphorylation of RAP74 by TAFII250 may provide a mechanism for signaling between components within the initiation complex to regulate transcription