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Evidence that Lin28 stimulates translation by recruiting RNA helicase A to polysomes.

ABSTRACT: The stem cell protein Lin28 functions to inhibit the biogenesis of a group of miRNAs but also stimulates the expression of a subset of mRNAs at the post-transcriptional level, the underlying mechanism of which is not yet understood. Here we report the characterization of the molecular interplay between Lin28 and RNA helicase A (RHA) known to play an important role in remodeling ribonucleoprotein particles during translation. We show that reducing Lin28 expression results in decreased RHA association with polysomes while increasing Lin28 expression leads to elevated RHA association. Further, the carboxyl terminus of Lin28 is necessary for interaction with both the amino and carboxyl termini of RHA. Importantly, a carboxyl terminal deletion mutant of Lin28 that retains RNA-binding activity fails to interact with RHA and exhibits dominant-negative effects on Lin28-dependent stimulation of translation. Taken together, these results lead us to suggest that Lin28 may stimulate translation by actively recruiting RHA to polysomes.

SUBMITTER: Jin J

PROVIDER: S-EPMC3089476 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Evidence that Lin28 stimulates translation by recruiting RNA helicase A to polysomes.

Jin Jianyu J Jing Wei W Lei Xin-Xiang XX Feng Chen C Peng Shuping S Boris-Lawrie Kathleen K Huang Yingqun Y

Nucleic acids research 20110118 9

The stem cell protein Lin28 functions to inhibit the biogenesis of a group of miRNAs but also stimulates the expression of a subset of mRNAs at the post-transcriptional level, the underlying mechanism of which is not yet understood. Here we report the characterization of the molecular interplay between Lin28 and RNA helicase A (RHA) known to play an important role in remodeling ribonucleoprotein particles during translation. We show that reducing Lin28 expression results in decreased RHA associa ...[more]

PMID: 21247876

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Project description:The Pseudomonas aeruginosa type III secretion system (T3SS) is a primary virulence factor important for phagocytic avoidance, disruption of host cell signaling, and host cell cytotoxicity. ExsA is the master regulator of T3SS transcription. The expression, synthesis, and activity of ExsA is tightly regulated by both intrinsic and extrinsic factors. Intrinsic regulation consists of the well-characterized ExsECDA partner-switching cascade, while extrinsic factors include global regulators that alter exsA transcription and/or translation. To identify novel extrinsic regulators of ExsA, we conducted a transposon mutagenesis screen in the absence of intrinsic control. Transposon disruptions within gene PA2840, which encodes a homolog of the Escherichia coli RNA-helicase DeaD, significantly reduced T3SS gene expression. Recent studies indicate that E. coli DeaD can promote translation by relieving inhibitory secondary structures within target mRNAs. We report here that PA2840, renamed DeaD, stimulates ExsA synthesis at the posttranscriptional level. Genetic experiments demonstrate that the activity of an exsA translational fusion is reduced in a deaD mutant. In addition, exsA expression in trans fails to restore T3SS gene expression in a deaD mutant. We hypothesized that DeaD relaxes mRNA secondary structure to promote exsA translation and found that altering the mRNA sequence of exsA or the native exsA Shine-Dalgarno sequence relieved the requirement for DeaD in vivo. Finally, we show that purified DeaD promotes ExsA synthesis using in vitro translation assays. Together, these data reveal a novel regulatory mechanism for P. aeruginosa DeaD and add to the complexity of global regulation of T3SS.Although members of the DEAD box family of RNA helicases are appreciated for their roles in mRNA degradation and ribosome biogenesis, an additional role in gene regulation is now emerging in bacteria. By relaxing secondary structures in mRNAs, DEAD box helicases are now thought to promote translation by enhancing ribosomal recruitment. We identify here an RNA helicase that plays a critical role in promoting ExsA synthesis, the central regulator of the Pseudomonas aeruginosa type III secretion system, and provide additional evidence that DEAD box helicases directly stimulate translation of target genes. The finding that DeaD stimulates exsA translation adds to a growing list of transcriptional and posttranscriptional regulatory mechanisms that control type III gene expression.

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Evidence that Lin28 stimulates translation by recruiting RNA helicase A to polysomes.

Publications

Evidence that Lin28 stimulates translation by recruiting RNA helicase A to polysomes.

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