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Mature mRNA is selectively released from the nuclear matrix by an ATP/dATP-dependent mechanism sensitive to topoisomerase inhibitors.

1987; Elsevier BV; Volume: 262; Issue: 18 Linguagem: Inglês

10.1016/s0021-9258(18)47502-3

1083-351X

Heinz C. Schröder, Dieter TRÖLLTSCH, Ursula Friese, Michael Bachmann, Wernér E.G. Müller,

Estrogen and related hormone effects

Ovalbumin mRNA precursors were found to be almost quantitatively associated with the hen oviduct nuclear matrix.On the other hand, only one-third of the mature ovalbumin mRNA of whole nuclei was recovered in the nuclear matrix fraction.The binding of both the high molecular weight mRNA precursors and the mature-sized mRNA to the matrix displayed no difference in stability against salt, urea, or detergents.The mature mRNA, however, was found to be released selectively from the matrix by ATP.In contrast, the mRNA precursors remained completely bound to the nuclear substructure in the presence of ATP.Detachment of mRNA from the matrix also occurred in the presence of ADP, AMP plus pyrophosphate, or ATP analogs that contain nonhydrolyzable CY,@ and @,r bonds.Contrasting with the ATP-induced effect, addition of poly(A), ethidium bromide, or the copper chelator 1,lO-phenanthroline to oviduct cell matrices caused an unspecific liberation of both mature and immature ovalbumin messengers.The release of the mature mRNA by ATP was found to be strongly inhibited by both nonintercalative and intercalative inhibitors of type I1 topoisomerase.These results suggest (i) that the selection of the mature mRNAs for nucleocytoplasmic transport occurs at the release stage from the matrix (Le.before translocation through the nuclear pore) and (ii) that reactions hitherto known to cause changes in the DNA secondary structure are associated with the detachment of mRNA from the nuclear substructure.Transport of mRNA from nucleus to cytoplasm is an ATPor GTP-dependent process which is thought to be mediated by a nuclear envelope-bound NTPase that is stimulated by poly(A) (for reviews, see Agutter, 1986; Schroder et al., 1987).This enzyme can be solubilized by Triton and purified to homogeneity (Schroder et al., 1986b).Experimental evidence, however, suggests that the NTPase and also other membranebound components of the nuclear envelope mRNA translocation apparatus cannot be solely responsible for nuclear RNA restriction since most of the nuclear RNA is still bound to membrane-depleted nuclei obtained after Triton treatment