Xp54, the Xenopus homologue of human RNA helicase p54, is an integral component of stored mRNP particles in oocytes
Ladomery, M. , Wade, E. and Sommerville, J. (1997) Xp54, the Xenopus homologue of human RNA helicase p54, is an integral component of stored mRNP particles in oocytes. Nucleic Acids Research, 25 (5). pp. 965-973. ISSN 0305-1048
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Publisher's URL: http://nar.oxfordjournals.org/cgi/content/short/25...
In investigating the composition of stored (maternal) mRNP particles in Xenopus oocytes, attention has focussed primarily on the phosphoproteins pp60/56, which are Y-box proteins involved in a general packaging of mRNA. We now identify a third, abundant, integral component of stored mRNP particles, Xp54, which belongs to the family of DEAD-box RNA helicases. Xp54 was first detected by its ability to photocrosslink ATP. Subsequent sequence analysis identifies Xp54 as a member of a helicase subfamily which includes: human p54, encoded at a chromosomal breakpoint in the B-cell lymphoma cell line, RC-K8; Drosophila ME31B, encoded by a maternally-expressed gene, and Saccharomyces pombe Ste13, cloned by complementation of the sterility mutant ste13. Expression studies reveal that the gene encoding Xp54 is transcribed maximally at early oogenesis: no transcripts are detected in adult tissues, other than ovary. Using a monospecific antibody raised against native Xp54, its presence in mRNP particles is confirmed by immunoblotting fractions bound to oligo(dT)-cellulose and separated by rate sedimentation and buoyant density. On isolating Xp54 from mRNP particles, it is shown to possess an ATP-dependent RNA helicase activity. Possible functions of Xp54 are discussed in relation to the assembly and utilization of mRNP particles.
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