Dataset Information

Regulation of repertoire development through genetic control of DH reading frame preference.

ABSTRACT: In jawed vertebrates most expressed Ig H chains use only one of six possible D(H) reading frames. Reading frame (RF)1, the preferred reading frame, tends to encode tyrosine and glycine, whereas the other five RFs tend to be enriched for either hydrophobic or charged amino acids. Mechanisms proposed to favor use of RF1 include a preference for deletion over inversion that discourages use of inverted RF1, RF2, and RF3; sequence homology between the 5' terminus of the J(H) and the 3' terminus of the D(H) that promotes rearrangement into RF1; an ATG start site upstream of RF2 that permits production of a truncated Dmicro protein; stop codons in RF3; and, following surface expression of IgM, somatic, presumably Ag receptor-based selection favoring B cells expressing Igs with tyrosine- and glycine-enriched CDR-H3s. By creating an IgH allele limited to the use of a single, frameshifted DFL16.1 D(H) gene segment, we tested the relative contribution of these mechanisms in determining reading frame preference. Dmicro-mediated suppression via an allelic exclusion-like mechanism dominated over somatic selection in determining the composition of the CDR-H3 repertoire. Evidence of somatic selection for RF1-encoded tyrosine in CDR-H3 was observed, but only among the minority of recirculating, mature B cells that use D(H) in RF1. These observations underscore the extent to which the sequence of the D(H) acts to delimit the diversity of the Ab repertoire.

SUBMITTER: Zemlin M

PROVIDER: S-EPMC2680007 | biostudies-literature | 2008 Dec

REPOSITORIES: biostudies-literature

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Regulation of repertoire development through genetic control of DH reading frame preference.

Zemlin Michael M Schelonka Robert L RL Ippolito Gregory C GC Zemlin Cosima C Zhuang Yingxin Y Gartland G Larry GL Nitschke Lars L Pelkonen Jukka J Rajewsky Klaus K Schroeder Harry W HW

Journal of immunology (Baltimore, Md. : 1950) 20081201 12

In jawed vertebrates most expressed Ig H chains use only one of six possible D(H) reading frames. Reading frame (RF)1, the preferred reading frame, tends to encode tyrosine and glycine, whereas the other five RFs tend to be enriched for either hydrophobic or charged amino acids. Mechanisms proposed to favor use of RF1 include a preference for deletion over inversion that discourages use of inverted RF1, RF2, and RF3; sequence homology between the 5' terminus of the J(H) and the 3' terminus of th ...[more]

PMID: 19050259

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Project description:Translation of an mRNA in eukaryotes starts at AUG in most cases. Near-cognate codons (NCCs) such as UUG, ACG and AUU are also used as start sites at low levels in S. cerevisiae. Initiation from NCCs or AUGs in the 5’-untranslated regions (UTRs) of mRNAs can lead to translation of upstream open reading frames (uORFs) that might regulate expression of the main ORF (mORF). Although there is some circumstantial evidence that the translation of uORFs can be affected by environmental conditions, little is known about how it is affected by changes in growth temperature. Using reporter assays, we found that changes in growth temperature can affect translation from NCC start sites in yeast cells, suggesting the possibility that gene expression could be regulated by temperature by altering use of different uORF start codons. Using ribosome profiling, we provide evidence that growth temperature regulates the efficiency of translation of nearly 200 uORFs in S. cerevisiae. Of these uORFs, most that start with an AUG codon have increased translational efficiency at 37 ˚C relative to 30 ˚C and decreased efficiency at 20 ˚C. For translationally regulated uORFs starting with NCCs, we did not observe a general trend for the direction of regulation as a function of temperature, suggesting mRNA-specific features can determine the mode of temperature-dependent regulation. Consistent with this conclusion, the position of the uORFs in the 5’-leader relative to the 5’-cap and the start codon of the main ORF correlates with the direction of temperature-dependent regulation of uORF translation. We have identified several novel cases in which changes in uORF translation are inversely correlated with changes in the translational efficiency of the downstream main ORF. Our data suggest that translation of these mRNAs is subject to temperature-dependent, uORF-mediated regulation. Overall, our data suggest that alterations in the translation of specific uORFs by temperature can regulate gene expression in S. cerevisiae.

Project description:BACKGROUND:Translation of an mRNA in eukaryotes starts at an AUG codon in most cases, but near-cognate codons (NCCs) such as UUG, ACG, and AUU can also be used as start sites at low levels in Saccharomyces cerevisiae. Initiation from NCCs or AUGs in the 5'-untranslated regions (UTRs) of mRNAs can lead to translation of upstream open reading frames (uORFs) that might regulate expression of the main ORF (mORF). Although there is some circumstantial evidence that the translation of uORFs can be affected by environmental conditions, little is known about how it is affected by changes in growth temperature. RESULTS:Using reporter assays, we found that changes in growth temperature can affect translation from NCC start sites in yeast cells, suggesting the possibility that gene expression could be regulated by temperature by altering use of different uORF start codons. Using ribosome profiling, we provide evidence that growth temperature regulates the efficiency of translation of nearly 200 uORFs in S. cerevisiae. Of these uORFs, most that start with an AUG codon have increased translational efficiency at 37 °C relative to 30 °C and decreased efficiency at 20 °C. For translationally regulated uORFs starting with NCCs, we did not observe a general trend for the direction of regulation as a function of temperature, suggesting mRNA-specific features can determine the mode of temperature-dependent regulation. Consistent with this conclusion, the position of the uORFs in the 5'-leader relative to the 5'-cap and the start codon of the main ORF correlates with the direction of temperature-dependent regulation of uORF translation. We have identified several novel cases in which changes in uORF translation are inversely correlated with changes in the translational efficiency of the downstream main ORF. Our data suggest that translation of these mRNAs is subject to temperature-dependent, uORF-mediated regulation. CONCLUSIONS:Our data suggest that alterations in the translation of specific uORFs by temperature can regulate gene expression in S. cerevisiae.

Dataset Information

Regulation of repertoire development through genetic control of DH reading frame preference.

Publications

Regulation of repertoire development through genetic control of DH reading frame preference.

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