The 5'-untranslated RNA of the human dhfr minor transcript alters transcription pre-initiation complex assembly at the major (core) promoter.
The human dhfr minor transcript is distinguished from the predominant dhfr mRNA by an approximately 400 nucleotide extension of the 5'-untranslated region, which corresponds to the major (core) promoter DNA (its template). Based on its unusual sequence composition, we hypothesized that the minor transcript 5'-UTR might be capable of altering transcription pre-initiation complex assembly at the core promoter, through direct interactions of the RNA with specific regulatory polypeptides or the promoter DNA itself. We found that the minor transcript 5'-UTR selectively sequesters transcription factor Sp3, and to a lesser extent Sp1, preventing their binding to the dhfr core promoter. This allows a third putative transcriptional regulatory protein, which is relatively resistant to sequestration by the minor transcript RNA, the opportunity to bind the dhfr core promoter. The selective sequestration of Sp3 > Sp1 by the minor transcript 5'-UTR involves an altered conformation of the RNA, and a structural domain of the protein distinct from that required for binding to DNA. As a consequence, the minor transcript 5'-UTR inhibits transcription from the core promoter in vitro (in trans) in a concentration-dependent manner. These results suggest that the dhfr minor transcript may function in vivo (in cis) to regulate the transcriptional activity of the major (core) promoter.
Blume
Scott W
SW
Department of Medicine and Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA. scott.blume@ccc.uab.edu
Meng
Zheng
Z
Shrestha
Kedar
K
Snyder
Richard C
RC
Emanuel
Peter D
PD
D020121:5' Untranslated Regions; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D051705:Sp3 Transcription Factor; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D016335:Zinc Fingers
D020121:5' Untranslated Regions; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C497121:SP3 protein, human; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051705:Sp3 Transcription Factor; D004247:DNA; D013762:Tetrahydrofolate Dehydrogenase; D003850:Deoxyribonuclease I