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Description: To examine endogenous mPP localization, we used m-TAG to create strains tagged with the MS2L sequence (Table S1). We first localized mRNAs encoding proteins involved in peroxisome biogenesis, called peroxins (PEX1-3, 5-8, 10-15, 17, 19, 21, 22, 27-30, and 32). On the expression of MS2-CP-GFP(x3) in cells bearing the tagged genes, we observed that few had fluorescent RNA granules when grown on glucose-containing medium. But when grown under conditions that induce peroxisome proliferation (i.e., media containing oleate), we saw a large increase in the number of cells bearing fluorescent granules. We then determined that between 56% and 80% of granules seen in the MS2L-tagged PEX1, 5, 8, 11, 12, 13, 14, or 15 strains colocalized with peroxisomes labeled with a peroxisomal matrix marker, RFP-PTS1 (68%, 56%, 66%, 80%, 58%, 78%, 60%, and 78% colocalization, respectively; Fig. 1A and Table S2). Thus, mPPs associate with peroxisomes, although we noted that the number of RFP-labeled peroxisomes observed per cell (2-6) was usually greater than the number of granules (1-3). This may indicate that mPPs are in transient/intermittent association with peroxisomes, or that there are distinct (i.e., mature) peroxisomes that do not associate with mRNA. Data are collected from Table S2.
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