MCB Accepts, published online ahead of print on 2 September 2008

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Mol. Cell. Biol. doi:10.1128/MCB.00448-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

TRF4 is involved in polyadenylation of snRNAs in Drosophila melanogaster

Ryoichi Nakamura, Ryo Takeuchi, Kei-ichi Takata, Kaori Shimanouchi, Yoko Abe, Yoshihiro Kanai, Tatsushi Ruike, Ayumi Ihara, and Kengo Sakaguchi^*

Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi Chiba-ken, 278-8510, Japan; Department of Pharmacology, Hillman Cancer Center, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania 15213-1863, USA

^* To whom correspondence should be addressed. Email: kengo{at}rs.noda.tus.ac.jp.

The Saccharomyces cerevisiae poly(A) polymerases Trf4 and Trf5 are involved in an RNA quality control mechanism, where polyadenylated RNAs are degraded by the nuclear exosome. Although Trf4/5 homologue genes are distributed throughout multicellular organisms, their biological roles remain to be elucidated. Here we isolated the two homologues of Trf4/5 in Drosophila melanogaster, named DmTRF4-1 and DmTRF4-2, and investigated their biological function. DmTRF4-1 displayed poly(A) polymerase activity in vitro, whereas DmTRF4-2 did not. Gene knockdown of DmTRF4-1 by RNAi is lethal in flies, as is the case for the trf4 trf5 double mutants. By contrast, disruption of DmTRF4-2 results in viable flies. Cellular localization analysis suggested that DmTRF4-1 localizes in the nucleolus. Abnormal polyadenylation of snRNAs was observed in transgenic flies overexpressing DmTRF4-1, and was slightly increased by the suppression of DmRrp6, the 3'-5' exonuclease of the nuclear exosome. These results suggest that DmTRF4-1 and DmRrp6 are involved in the polyadenylation-mediated degradation of snRNAs in vivo.