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Mycoplasma hyorhinis vlp gene transcription: critical role in phase variation and expression of surface lipoproteins
Author(s) -
Citti Christine,
Wise Kim S.
Publication year - 1995
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1995.mmi_18040649.x
Subject(s) - biology , gene , genetics , tandem repeat , phenotype , locus (genetics) , gene expression , phase variation , transcription (linguistics) , microbiology and biotechnology , genome , linguistics , philosophy
Mycoplasma hyorhinis contains clustered vlp genes encoding v ariable l ipo p roteins (Vlps), the major coat proteins and surface antigens of this wall‐less prokaryotic pathogen. vlp genes are subject to discrete, high frequency mutations independently affecting the size or the expression of variant Vlp products. Change in Vlp size occurs by mutations altering the number of tandem intragenic repeats at the 3′ end of each single‐copy vlp gene. In this report, phase‐variant Vlp expression is shown to result from altered vlp gene transcription. vlpA, vlpB and vlpC transcripts were monitored in a clonal lineage selected to display various Vlp phenotypes. Each vlp gene was expressed as a distinct transcript, which was subject to drastic ON/OFF switches associated with random insertion/ deletion mutations in a homopolymeric tract of adenine residues in the promoter region of all vlp genes. Unexpectedly, the level of vlp transcripts appeared to depend on the length of the corresponding genes in the ON configuration. Higher proportional levels of shorter vlp transcripts were shown to reflect a greater abundance of short Vlp lipoproteins present in l ‐[ 35 S]‐cysteine‐labelled membrane protein preparations. The vlp cluster provides a heritable, and highly mutable, locus for the generation of surface diversity through random promoter mutations affecting the expression of genes, whose products also vary in length and abundance, by virtue of separate mutations in structural regions of the genes.