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Mol Biol Cell July 1, 2014; 25 (13): 2094-104.

Drosha protein levels are translationally regulated during Xenopus oocyte maturation.

Muggenhumer D , Vesely C , Nimpf S , Tian N , Yongfeng J , Jantsch MF .

MicroRNAs (miRNAs) are ∼21-nucleotide-long, single-stranded noncoding RNAs that regulate gene expression. Biogenesis of miRNAs is mediated by the two RNase III-like enzymes, Drosha and Dicer. Here we study miRNA biogenesis during maturation of Xenopus oocytes to eggs using microinjection of pri-miRNAs. We show that processing of exogenous and endogenous primary miRNAs (pri-miRNAs) is strongly enhanced upon maturation of oocytes to eggs. Overexpression of cloned Xenopus Drosha in oocytes, however, boosts pri-miRNA processing dramatically, indicating that Drosha is a rate-limiting factor in Xenopus oocytes. This developmental regulation of Drosha is controlled by poly(A) length addition to the Drosha mRNA, which boosts translation upon transition from oocytes to eggs. Processing of pri-miRNAs by Drosha and Dicer has been shown to be affected by adenosine-to-inosine deamination-type RNA editing. Using activated Xenopus eggs for microinjection experiments, we demonstrate that RNA editing can reduce pri-miRNA processing in vivo. This processing block is determined by the structural but not sequence changes introduced by RNA editing.

PubMed ID: 24829383
PMC ID: PMC4072582
Article link: Mol Biol Cell

Species referenced: Xenopus
Genes referenced: dicer1 drosha myc nucb1 smn1 tff3.7

Article Images: [+] show captions
References [+] :
Armisen, Abundant and dynamically expressed miRNAs, piRNAs, and other small RNAs in the vertebrate Xenopus tropicalis. 2009, Pubmed, Xenbase