Characterization of the "Yarrowia lipolytica YlSRP72" gene, a component of the yeast signal recognition particle

Resumen

The Yarrowia lipolytica SRP72 gene product (YlSRP72), a homolog of the 72-kDa subunit of the mammalian SRP, encodes a putative protein of 602 amino acids. Northern blot analysis revealed a unique YlSRP72-specific transcript of 1.8 kb. The deduced amino acid sequence showed higher identities with the Srp72 proteins of euascomycetes than with hemiascomycetes. Chromosomal hybridization experiments showed that the YlSRP72 gene is located in chromosome V of the standard E150 strain of Y. lipolytica. Fluorescent microscopy revealed that the YlSRP72-GFP fusion protein was expressed in the cytoplasm and nucleus. The YlSRP72 gene was interrupted by the pop-out method; however, deletion of the gene proved to be lethal. This is in contrast to the results described for the Saccharomyces cerevisiae SRP72 gene, which is not essential for cell growth, and supports our previous finding with another component of the yeast recognition particle, YlSEC65. The present work suggests that SRP-dependent targeting is the main secretory pathway in Y. lipolytica, as has been described for higher eukaryotes.