Variable region V1 of Saccharomyces cerevisiae 18S rRNA participates in biogenesis and function of the small ribosomal subunit |
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Authors: | RW van Nues J Venema RJ Planta HA Raué |
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Affiliation: | Department of Biochemistry and Molecular Biology, IMBW, BioCentrum Amsterdam, Vrije Universiteit, de Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands. |
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Abstract: | The role of helix 6, which forms the major portion of the most 5'-located expansion segment of Saccharomyces cerevisiae 18S rRNA, was studied by in vivo mutational analysis. Mutations that increased the size of the helical part and/or the loop, even to a relatively small extent, abolished 18S rRNA formation almost completely. Concomitantly, 35S pre-rRNA and an abnormal 23S precursor species accumulated. rDNA units containing these mutations did not support cell growth. A deletion removing helix 6 almost completely, on the other hand, had a much less severe effect on the formation of 18S rRNA, and cells expressing only the mutant rRNA remained able to grow, albeit at a much reduced rate. Disruption of the apical A.U base pair by a single point mutation did not cause a noticeable reduction in the level of 18S rRNA but did result in a twofold lower growth rate of the cells. This effect could not be reversed by introduction of a second point mutation that restores base pairing. We conclude that both the primary and the secondary structure of helix 6 play an important role in the formation and the biological function of the 40S subunit. |
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