R P Hyde-DeRuyscher | PubMed Health

PubMed1995

DNA binding sites for the transcriptional activator/repressor YY1.

YY1 is ubiquitously expressed zinc finger DNA binding protein. It can act as a transcriptional repressor or activator and, when binding at the initiator element, as a component of the basal transcription complex. Binding sites for YY1 have been reported in a wide variety of promoters and they exhibit substantial diversity in their sequence. To better understand how YY1 interacts with DNA and to be able to predict the presence of YY1 sites in a more comprehensive fashion, we have selected YY1 binding sites from a random pool of oligonucleotides. The sites display considerable heterogeneity, but contain a conserved 5'-CAT-3' core flanked by variable regions, generating the consensus 5'-(C/g/a)(G/t)(C/t/a)CATN(T/a)(T/g/c)-3', where the upper case letters represent the preferred base. This high degree of flexibility in DNA recognition can be predicted by modeling the interaction of the four YY1 zinc fingers with DNA and a detailed model for this interaction is presented and discussed.

Amino Acid Sequence↗

PubMed1990

Polyomavirus late pre-mRNA processing: DNA replication-associated changes in leader exon multiplicity suggest a role for leader-to-leader splicing in the early-late switch.

Polyomavirus late mRNAs contain at their 5' ends multiple, tandem repeats of a 57-base noncoding sequence, the late leader, whose sequence appears only once in the viral genome. Pre-mRNA molecules are processed by a pathway that includes the splicing of late leader exons to each other in giant, multigenome-length precursors which are the result of inefficient transcription termination. We have devised a method involving reverse transcription and the polymerase chain reaction to determine the number of tandem late leader units on polyomavirus late RNA molecules. Using this technique, we have shown that each class of late viral mRNA (mVP1, mVP2, and mVP3) consists of molecules with between 1 and 12 tandem leader units at their 5' ends. Importantly, single-leader RNAs are underrepresented in both the cytoplasm and the nucleus, suggesting that single-leader primary transcripts are preferentially degraded in the nucleus. In addition, the average number of leaders on late RNAs increases in the presence of DNA replication. Taken together with previous work from our laboratory, the results presented here are consistent with a model for the control of late gene expression at the level of RNA splicing and stability which is in turn controlled by the efficiency of transcription termination.

Animals↗