XPO5 promotes primary miRNA processing independently of RanGTP

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• Exportin 5 (XPO5) is known to mediate the nuclear export of microRNA (miRNA) precursors in a RanGTP-dependent manner.
• The full spectrum of RNA species associated with XPO5 and its potential functions beyond nuclear export remain largely undetermined.

Purpose of the Study:

• To globally identify RNA species bound by XPO5.
• To investigate potential novel functions of XPO5 in RNA processing and cellular regulation.
• To elucidate the physiological significance of XPO5 in mammalian development.

Main Methods:

• RNA immunoprecipitation coupled with sequencing (RIP-Seq) to identify XPO5-bound RNAs.
• In vitro assays to assess XPO5 binding to various RNA structures.
• Analysis of miRNA processing efficiency in the presence and absence of XPO5.
• Generation and analysis of XPO5 knockout mouse models.

Main Results:

• XPO5 extensively binds to double-stranded RNA regions in clustered primary miRNA (pri-miRNA) precursors and various cellular RNAs, including vault RNAs.
• XPO5 binding to certain pri-miRNAs and structured RNAs is independent of RanGTP.
• XPO5 significantly enhances the processing efficiency of specific pri-miRNAs (e.g., pri-mir-19a, pri-mir-15b~16-2) by the DROSHA/DGCR8 microprocessor complex.
• Genetic deletion of XPO5 severely impairs miRNA biogenesis and leads to significant defects in mouse embryonic development and skin morphogenesis.

Conclusions:

• XPO5 possesses an uncharacterized function in recognizing and facilitating the nuclear cleavage of clustered pri-miRNAs.
• This study identifies a broad range of cellular RNAs interacting with XPO5.
• XPO5 plays critical physiological roles in mouse development, extending beyond its established function in nuclear export.