Polyadenylation of ribosomal RNA by Candida albicans also involves the small subunit - PubMed (original) (raw)

Polyadenylation of ribosomal RNA by Candida albicans also involves the small subunit

Jacob Fleischmann et al. BMC Mol Biol. 2004.

Abstract

Background: Candida albicans is a polymorphic fungus causing serious infections in immunocompromised patients. It is capable of shifting from yeast to germinating forms such as hypha and pseudohypha in response to a variety of signals, including mammalian serum. We have previously shown that some of the large 25S components of ribosomal RNA in Candida albicans get polyadenylated, and this process is transiently intensified shortly after serum exposure just prior to the appearance of germination changes.

Results: We now present data that this process also involves the small 18S subunit of ribosomal RNA in this organism. Unlike the large 25S subunit, polyadenylation sites near the 3' end are more variable and no polyadenylation was found at the reported maturation site of 18S. Similar to 25S, one or more polyadenylated mature sized 18S molecules get intensified transiently by serum just prior to the appearance of hypha.

Conclusions: The transient increase in polyadenylation of both the large and the small subunits of ribosomal RNA just prior to the appearance of hypha, raises the possibility of a role in this process.

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Figures

Figure 1

Figure 1

Polyadenylation sites of 18S rRNA subunit and a full length polyadenylated 18S clone. Polyadenylation positions on 18S subunit. (A) represents the clones derived from amplification with primers designed for the 3'end of 18S. Underlined letters represent polyadenylation sites. Y or S over them indicate whether RNA came from yeast exposed to YPD (Y) or serum (S) and superscripted digits over them indicate the number of clones found at that position. The bold enlarged letters represent the sequence with the most polyadenylation sites. The #1624 represents the position from 5' end of 18S. (B) represents partial sequences at the 5' and 3' ends of a full length clone of a polyadenylated 18S molecule.

Figure 2

Figure 2

Upregulation of 18S rRNA polyadenylation by serum exposure. Northern blot of poly-A selected RNA hybridized by 18S and _UB_14 specific probes (A). (a) is RNA derived from cells grown in YEPD at 30°C, (b) is RNA from yeast in serum for 5 minutes at 37°C, and (c) is RNA from yeast in serum for 15 minutes at the same temperature. (B) represents the quantitative phosphorimager data of the Northern shown in (A). Small letters (a, b, c) are the same as in (A).

Figure 3

Figure 3

Real-time PCR confirmation of 18S rRNA polyadenylation upregulation by serum. Real-time PCR reactions represented as PCR baseline subtracted relative fluorescence units (RFU) versus cycle number plots. Triangles represent reactions with 18S specific primers and circles represent reactions with 5S specific primers.

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