title: RpS3 translation is repressed by interaction with its own mRNA.
abstract: Ribosomal protein S3 (RpS3) is a well-known multi-functional protein mainly involved in protein biosynthesis as a member of the small ribosomal subunit. It also plays a role in repairing various DNA damage acting as a repair UV endonuclease. Most of the rpS3 pool is located in the ribosome while the minority exists in free form in the cytoplasm. We here report an additional function of rpS3 in which it represses its own translation by binding to its cognate mRNA. Through RT-PCR of the RNAs co-immunoprecipitated with ectopically expressed rpS3, rpS3 protein was found to interact with various RNAs-endogenous rpS3, 18S rRNA. The S3-C terminal domain was shown to be the major mRNA binding domain of rpS3, independent of the KH domain. This interaction was shown to occur in cytoplasmic fractions rather than ribosomal fractions, and then is involved in its own mRNA translational inhibition by in vitro translation. Furthermore, when Flag-tagged rpS3 was transiently transfected into 293T cells, the level of endogenous rpS3 gradually decreased regardless of transcription. These results suggest that free rpS3 regulates its own translation via a feedback mechanism.
authors.affiliation: Laboratory of Biochemistry, School of Life Sciences and Biotechnology, and BioInstitute, Korea University, Seoul, South Korea.
authors.forename: Hag Dong
authors.initials: HD
authors.lastname: Kim
authors.forename: Tae-Sung
authors.initials: TS
authors.lastname: Kim
authors.forename: Yoo Jin
authors.initials: YJ
authors.lastname: Joo
authors.forename: Hyun-Seock
authors.initials: HS
authors.lastname: Shin
authors.forename: Sang-Hwa
authors.initials: SH
authors.lastname: Kim
authors.forename: Chang-Young
authors.initials: CY
authors.lastname: Jang
authors.forename: Cheol Eui
authors.initials: CE
authors.lastname: Lee
authors.forename: Joon
authors.initials: J
authors.lastname: Kim
mesh_terms: D001483:Base Sequence; D003600:Cytosol / Q000378:metabolism; D017931:DNA Primers; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012269:Ribosomal Proteins / Q000235:genetics* / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism
chemical_list: D017931:DNA Primers; D012333:RNA, Messenger; D012269:Ribosomal Proteins; C044152:ribosomal protein S3