title: Evidence for post-transcriptional regulation of clustered microRNAs in Drosophila.
abstract: BACKGROUND
  MicroRNAs (miRNA) are short 21-23nt RNAs capable of inhibiting translation of complementary target messenger RNAs. Almost half of D. melanogaster miRNA genes are grouped in genomic clusters.
  
  
  RESULTS
  The peculiarities of the expression of clustered miRNAs were studied using publicly available libraries of sequenced small RNAs from different Drosophila tissues. We have shown that although miRNAs from almost all clusters have similar tissue expression profiles (coordinated clusters), some clusters contain miRNAs with uncoordinated expression profiles. The predicted transcription start sites (TSSs) of such clusters are located upstream of the first miRNA, but no TSSs are found within the clusters. The expression profiles of miR and miR* sequences in uncoordinated clustered miRNAs do not correlate while their profiles from the coordinated clustered miRNAs are similar.
  
  
  CONCLUSIONS
  The presence of exclusively upstream promoters in miRNA clusters containing uncoordinated miRNAs means that the clusters are transcribed as single transcription units. The difference of tissue expression profiles of uncoordinated miRNAs and the corresponding miRs* suggests a post-transcriptional regulation of their processing or stability.
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, Russia. ryazansky@img.ras.ru
authors.forename: Sergei S
authors.initials: SS
authors.lastname: Ryazansky
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Gvozdev
authors.forename: Eugene
authors.initials: E
authors.lastname: Berezikov
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics*; D020869:Gene Expression Profiling; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism*; D005810:Multigene Family; D011401:Promoter Regions, Genetic; D012323:RNA Processing, Post-Transcriptional; D024363:Transcription Initiation Site
chemical_list: D035683:MicroRNAs