Nuclear accumulation of S-adenosylhomocysteine hydrolase in transcriptionally active cells during development of Xenopus laevis

Citation
N. Radomski et al., Nuclear accumulation of S-adenosylhomocysteine hydrolase in transcriptionally active cells during development of Xenopus laevis, MOL BIOL CE, 10(12), 1999, pp. 4283-4298
Citations number
57
Categorie Soggetti
Cell & Developmental Biology
Journal title
MOLECULAR BIOLOGY OF THE CELL
ISSN journal
10591524 → ACNP
Volume
10
Issue
12
Year of publication
1999
Pages
4283 - 4298
Database
ISI
SICI code
1059-1524(199912)10:12<4283:NAOSHI>2.0.ZU;2-S
Abstract
The oocyte nuclear antigen of the monoclonal antibody 32-5B6 of Xenopus lae vis is subject to regulated nuclear translocation during embryogenesis. It is distributed in the cytoplasm during oocyte maturation, where it remains during cleavage and: blastula stages, before it gradually reaccumulates in the nuclei during gastrulation, We have now identified this antigen to be t he enzyme S-adenosylhomocysteine hydrolase (SAHH). SAHH is the only enzyme that cleaves S-adenosylhomocysteine, a reaction product and an inhibitor of all S-adenosylmethionine-dependent methylation reactions. We have compared the spatial and temporal patterns of nuclear localization of SAHH and of n uclear methyltransferase activities during embryogenesis and in tissue cult ure cells. Nuclear localization of Xenopus SAHH did not temporally correlat e with DNA methylation. However, we found that SAHH nuclear localization co incides with high rates of mRNA synthesis, a subpopulation colocalizes With RNA polymerase II, and inhibitors of SAHH reduce both methylation and synt hesis of poly(A)(+) RNA. We therefore propose that accumulation of SAHH in the nucleus may be required for efficient cap methylation in transcriptiona lly active cells. Mutation analysis revealed that the C terminus and the N terminus are both required for efficient nuclear translocation in tissue cu lture cells, indicating that more than one interacting domain contributes t o nuclear accumulation of Xenopus SAHH.