High impact information on 42Sp50

• 42Sp50 is the major protein component of a 42S nucleoprotein particle that is very abundant in previtellogenic oocytes of X. laevis, 42Sp50 differs from EF-1 alpha O not only by its amino acid sequence, but also by several properties already reported [1].
• 42Sp48 in previtellogenic Xenopus oocytes is structurally homologous to EF-1 alpha and may be a stage-specific elongation factor [2].
• Direct assays of both 42S fractions and purified 42S p48 show that this cross-reactivity is of functional significance since 42S p48, like EF-1 alpha, can transfer charged amino acids to ribosomes [3].
• We further demonstrate that 42S p48 is degraded soon after the onset of vitellogenesis, while the EF-1 alpha concentration remains essentially unchanged during this transition [3].
• Although germ cells contain very little eEF-1 alpha S mRNA, several eEF-1 alpha S retropseudogenes exist in X. laevis chromosomes [4].

Biological context of 42Sp50

• A major function served by 42Sp50 appears to be the storage of tRNAs for later use in oogenesis and early embryogenesis [5].
• The 42S RNP particle consists of various tRNAs, 5S RNA, 42Sp50 and a 5S RNA binding protein (42Sp43) [5].
• In situ hybridization was used to follow the distribution of the mRNAs encoding the somatic form of elongation factor 1 alpha (EF-1 alpha S) and the germinal counterparts of this factor, thesaurin a and EF-1 alpha O, throughout metamorphosis in the gonads of Xenopus laevis tadpoles [6].
• We suggest that eEF-1 alpha S pseudogenes are generated in primordial germ cells of the embryo before they differentiate into oogonia or spermatogonia [4].
• Elongation factor 1 alpha (EF-1 alpha) is concentrated in the Balbiani body and accumulates coordinately with the ribosomes during oogenesis of Xenopus laevis [7].

Anatomical context of 42Sp50

• In contrast, another form of eEF-1 alpha (eEF-1 alpha O) mRNA is highly concentrated in oogonia and in previtellogenic oocytes but is undetectable in eggs and embryos. eEF-1 alpha O mRNA is also present in spermatogonia and spermatocytes of adult testis [4].
• Moreover EF-1 alpha mRNA, similarly to rp-mRNAs, is always localized on mRNP or fully loaded on polysomes but never on small polysomes [8].
• We have then compared the translation pattern of EF-1 alpha and rp-mRNAs during Xenopus embryogenesis and in Xenopus cultured cells during growth rate changes [8].
• Following the blastula stage there is a sharp increase in the amount of EF1-alpha mRNA [9].

Associations of 42Sp50 with chemical compounds

• 1) Both stimulate elongation factor 1 alpha-mediated transfer RNA binding to ribosomes and exchange of guanine nucleotides on elongation factor 1 alpha to a comparable degree [10].
• The 5' end of EF-1 alpha mRNA, examined by primer extension, revealed the presence of a terminal pyrimidine tract that is characteristic of ribosomal protein mRNAs (rp-mRNAs) [8].

Analytical, diagnostic and therapeutic context of 42Sp50

• Southern-blot analysis of genomic DNA suggests that, besides the two closely related EF-1 alpha genes investigated in this study, other more-distantly related genes may exist in the X. laevis genome [11].
• Transcription of EF-1 alpha genes during oogenesis and embryonic development was studied by Northern-blot analysis and by in situ hybridizations [11].

References