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Micro RNAs (miRNAs) are short non-coding RNAs which
play roles in post-transcriptional regulation via sequence complementarity
with mRNA transcripts. We have begun to investigate whether miRNAs
post-transcriptionally regulate the induction and progression of
meiosis in S. cerevisiae. This possibility is suggested by the presence
of short (16-18 bp) sequences in the introns of meiosis-specific
genes which are present within other genes and in non-coding regions
between genes, some of which have clear meiotic roles. Introns in
9 meiotic genes contain ~40 unique 16-18 bp sequences which we have
found in 18 genes and 33 intergenic regions in the S. cerevisiae
genome. These intronic sequences may be processed into miRNAs after
intron splicing or may themselves be targets for miRNA binding.
Such sequences within and near genes are candidate miRNA binding
sites, and those more distant from flanking genes are candidates
for independently transcribed miRNAs. Using PCR amplification, molecular
cloning, and sequencing we have created probes which contain the
sequences of interest and the termini of their flanking genes. These
are being used as probes on Northern blots of total RNA isolated
from S. cerevisiae at sequential time points during meiosis. From
these experiments, we will investigate correlations in the expression
of the flanking genes with known meiotic genes and attempt to detect
the presence of free-standing miRNAs.
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