Repression of gene expression by an exogenous sequence element acting in concert with a heterogeneous nuclear ribonucleoprotein-like protein, Nrd1, and the putative helicase Sen1.
We have fortuitously identified a nucleotide sequence that decreases expression of a reporter gene in the yeast Saccharomyces cerevisiae 20-fold when inserted into an intron. The primary effect of the insertion is a decrease in pre-mRNA abundance accompanied by the appearance of 3'-truncated transcripts, consistent with premature transcriptional termination and/or pre-mRNA degradation. Point mutations in the cis element relieve the negative effect, demonstrating its sequence specificity. A novel yeast protein, named Nrd1, and a previously identified putative helicase, Sen1, help mediate the negative effect of the cis element. Sen1 is an essential nuclear protein that has been implicated in a variety of nuclear functions. Nrd1 has hallmarks of a heterogeneous nuclear ribonucleoprotein, including an RNA recognition motif, a region rich in RE and RS dipeptides, and a proline- and glutamine-rich domain. An N-terminal domain of Nrd1 may facilitate direct interaction with RNA polymerase II. Disruption of the NRD1 gene is lethal, yet C-terminal truncations that delete the RNA recognition motif and abrogate the negative effect of the cis element nevertheless support cell growth. Thus, expression of a gene containing the cis element could be regulated through modulation of the activity of Nrd1. The recent identification of Nrd1-related proteins in mammalian cells suggests that this potential regulatory pathway is widespread among eukaryotes.
Steinmetz
E J
EJ
Department of Biomolecular Chemistry, University of Wisconsin Medical School, Madison 53706-1532, USA.
Brow
D A
DA
D000595:Amino Acid Sequence; D004265:DNA Helicases; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D009154:Mutation; D020365:RNA Helicases; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment
D005656:Fungal Proteins; C491211:NRD1 protein, S cerevisiae; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; C542347:SEN1 protein, S cerevisiae; D004265:DNA Helicases; D020365:RNA Helicases