Characterization and subcellular localization of ribonuclease H activities from Xenopus laevis oocytes.
Ribonuclease H activities present in fully grown Xenopus oocytes were investigated by using either liquid assays or renaturation gel assays. Whereas the test in solution detected an apparently unique class I ribonuclease H activity, the activity gels did not detect this enzyme but another one with the molecular weight expected for a class II ribonuclease H. The ribonuclease HI was found to be primarily concentrated in the germinal vesicle, but around 5% of this activity was detectged in the cytoplasm and may correspond to the activity involved in antisense oligonucleotide-mediated destruction of messenger RNAs. The concentration of this class I ribonuclease H in oocytes is similar to that in somatic cells. The class II ribonuclease H remained undetectable by the test in solution because its activity was cryptic. On activity gel, a polypeptide with the apparent molecular mass of 32 kDa, expected for a ribonuclease HII, was found to be concentrated in mitochondria although no RNase H activity could be detected by using the liquid assay. Based on sedimentation studies, we hypothesize that the apparent absence of RNase H activity in solution could be the result of the association of this 32-kDa polypeptide with other polypeptides, or possibly nucleic acids, to form a multimer of, until now, unknown function.
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Laboratoire de Biophysique Moléculaire, INSERM U386, Université de Bordeaux II, France.
Frank
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P
Toulme
J J
JJ
Büsen
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W
D000818:Animals; D008970:Molecular Weight; D009865:Oocytes / Q000201:enzymology* / Q000648:ultrastructure; D010455:Peptides / Q000032:analysis; D016914:Ribonuclease H / Q000032:analysis* / Q000378:metabolism; D014982:Xenopus laevis / Q000378:metabolism*
D010455:Peptides; D016914:Ribonuclease H