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Human ribosomal RNA variants from a single individual and their expression in different tissues.

ABSTRACT: We have investigated the extent of sequence variation in human ribosomal RNA (rRNA) genes and the expression of specific rRNA gene variants in different tissues of an individual. Focusing on the fifth variable region (V5; nt 2065-2244) of the 28S rRNA gene, we find that sequence differences between rRNA genes of a single individual are characterized by differences in number of repeats of simple sequences at four specific sites. These data support and extend previous findings which show similar V5 sequence variation in rRNA genes from a group of individuals. We performed experiments to determine if there is differential gene expression within the rRNA multigene family. From the analysis of data of six variant V5 probes protected from RNase digestion by rRNAs isolated from different tissues of the individual, we conclude that each variant rRNA is present in a similar proportion in these tissues, whereas the actual contributions of variants differ, their relative proportion is maintained from tissue to tissue in an individual. We favor the explanation of a gene dosage effect over that of a regulated gene effect to account for this pattern of rRNA gene expression. In addition, computer generated secondary structure models of each V5 clone structure predict the same three helix structure with the regions of sequence variation contained in one stem-loop structure.

SUBMITTER: Kuo BA

PROVIDER: S-EPMC146304 | biostudies-other | 1996 Dec

REPOSITORIES: biostudies-other

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Human ribosomal RNA variants from a single individual and their expression in different tissues.

Kuo B A BA Gonzalez I L IL Gillespie D A DA Sylvester J E JE

Nucleic acids research 19961201 23

We have investigated the extent of sequence variation in human ribosomal RNA (rRNA) genes and the expression of specific rRNA gene variants in different tissues of an individual. Focusing on the fifth variable region (V5; nt 2065-2244) of the 28S rRNA gene, we find that sequence differences between rRNA genes of a single individual are characterized by differences in number of repeats of simple sequences at four specific sites. These data support and extend previous findings which show similar V ...[more]

PMID: 8972871

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Project description:BackgroundRibosomal proteins (RPs) have about 2000 pseudogenes in the human genome. While anecdotal reports for RP pseudogene transcription exists, it is unclear to what extent these pseudogenes are transcribed. The RP pseudogene transcription is difficult to identify in microarrays due to potential cross-hybridization between transcripts from the parent genes and pseudogenes. Recently, transcriptome sequencing (RNA-seq) provides an opportunity to ascertain the transcription of pseudogenes. A challenge for pseudogene expression discovery in RNA-seq data lies in the difficulty to uniquely identify reads mapped to pseudogene regions, which are typically also similar to the parent genes.ResultsHere we developed a specialized pipeline for pseudogene transcription discovery. We first construct a "composite genome" that includes the entire human genome sequence as well as mRNA sequences of real ribosomal protein genes. We then map all sequence reads to the composite genome, and only exact matches were retained. Moreover, we restrict our analysis to strictly defined mappable regions and calculate the RPKM values as measurement of pseudogene transcription levels. We report evidences for the transcription of RP pseudogenes in 16 human tissues. By analyzing the Human Body Map 2.0 study RNA-sequencing data using our pipeline, we identified that one ribosomal protein (RP) pseudogene (PGOHUM-249508) is transcribed with RPKM 170 in thyroid. Moreover, three other RP pseudogenes are transcribed with RPKM > 10, a level similar to that of the normal RP genes, in white blood cell, kidney, and testes, respectively. Furthermore, an additional thirteen RP pseudogenes are of RPKM > 5, corresponding to the 20-30 percentile among all genes. Unlike ribosomal protein genes that are constitutively expressed in almost all tissues, RP pseudogenes are differentially expressed, suggesting that they may contribute to tissue-specific biological processes.ConclusionsUsing a specialized bioinformatics method, we identified the transcription of ribosomal protein pseudogenes in human tissues using RNA-seq data.

Dataset Information

Human ribosomal RNA variants from a single individual and their expression in different tissues.

Publications

Human ribosomal RNA variants from a single individual and their expression in different tissues.

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