Transcript MicroRNA-Directed Cleavage of HOXB8 mRNA

MicroRNA-Directed
Cleavage of HOXB8 mRNA
Soraya Yekta,I-hung Shih, David P.Bartel
23 APRIL 2004 VOL 304 SCIENCE
Hox genes in mammals
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The vertebrate homeotic complex comprises
four distinct Hox gene clusters (Hox A, B, C, D)
that are organized into thirteen homology
The chromosomal organization of the genes in
each Hox cluster reflects its anterior-posterior
expression in the body plan (spatial colinearity).
In general, members of the same subgroup are
expressed at the same time and have the same
anterior boundary of expression
The current model for the biogenesis and post-transcription
suppression of microRNAs and siRNAs
Recent progress
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In plant, most miRNAs anneal to their
targets with nearly complete
complementarity at a single site,leading to
mRNAs cleavage and degradation
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The extent of complementarity between the
siRNA/miRNA and its target can determine
the mechanism of silencing
miR-196 in Vertebrate
The sequence and genomic context of the vertebrate miR-196 family
Bold: residues of the mature miRNA; Red: miRNAs validated by cloning.
Asterisks: perfectly conserved residues
Overview of the 5’ RACE Procedure
RNAse protection assay
Expression of miR-196 during mouse embryonic developmen
The Northern blot probes total RNA from 7-day, 11-day,
15-day, and 17-day mouse embryos (lanes 1–4, respectively)
M :33P-labeled RNA size markers
MiR-196–directed cleavage of HOXB8 mRNA(1)
black Absolutely conserved nucleotides;
red complementary site ; pink G:U wobble
MiR-196–directed cleavage of HOXB8 mRNA(2)
perfect antisense sequence of miR-196a: miR-196a-as
perfect antisense sequence of miR-1d: miR-1d-as
miR-1d expressed in skeletal muscle cells
MiR-196–directed cleavage of HOXB8 mRNA(3)
Additional HOX genes predicted to be
regulatory targets of miR-196(1)
Wide red bars extensive complementarity,
narrow bars seed matches,
Asterisks slightly relaxed seed matches that permit G:U wobble
Sequence alignment of the miR-196 complementary site, and
representative complementary seed and flanking regions in th
3´ UTRs of HOXC8 and HOXD8 genes.
Black:absolutely conserved nucleotides
Red: miR-196 complementary site and the seed
Pink:G:U wobbles
Additional HOX genes predicted to be
regulatory targets of miR-196(2)
Additional HOX genes predicted to be
regulatory targets of miR-196(3)
Discussion
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Transcriptional repression may also
involved
Genetic model of mRNA cleavage in vivo
The difference of miRNA and siRNA
The mechanism of miRNA function
Thank you!