Polyadenylation of Na(+)-K(+)-ATPase beta 1-subunit during early development of Xenopus laevis.
In fully grown Xenopus oocytes, the synthesis of beta-subunits is limiting for the formation of functional Na(+)-K(+)-adenosinetriphosphatase alpha/beta-complexes (Geering, K. FEBS Lett. 285: 189-193, 1991). In the present study, we show that during oocyte growth (from stage I to stage VI) alpha 1-, but not beta 1- or beta 3-isoform, mRNAs accumulate. In addition, beta-mRNAs are apparently sequestered in an untranslated pool in fully grown oocytes (stage VI). From fertilization to morulation, the total pools of alpha 1-, beta 1-, or beta 3-mRNAs vary little. Whereas polyadenylated [poly(A)+] alpha 1- and beta 3-isoform mRNAs did not change significantly, poly(A)+ beta 1-mRNA abundance increased three- to fourfold at morulation, accompanied by a parallel increase in beta 1-protein synthesis. After midblastula transition (i.e., at early gastrula) and during neurulation, poly(A)+ alpha 1- and beta 3-mRNAs accumulated rapidly, whereas poly(A)+ beta 1-mRNA accumulation was delayed by approximately 2 h, beginning only at early neurula. Our results indicate that 1) the abundance of poly(A)+ beta 1-mRNA is rate limiting during embryonic development for the assembly of alpha 1/beta 1-heterodimers, shown to be involved in the vectorial transport of sodium in kidney cells, and 2) the polyadenylation of beta 1-mRNA is a rate-limiting factor during morulation for the synthesis and assembly of new sodium pumps at the time of blastocoel fluid formation. The 3'-untranslated region of beta 1-mRNA (but not of alpha 1-mRNA) expresses cytoplasmic polyadenylation elements (CPEs) with the consensus sequence AXX-AUUUU(A/U)(A/U)(A/U). A role of CPE in the differential polyadenylation of alpha 1- and beta 1-mRNA is proposed.
Burgener-Kairuz
P
P
Institut de Pharmacologie et de Toxicologie, Université de Lausanne, Switzerland.
Corthesy-Theulaz
I
I
Merillat
A M
AM
Good
P
P
Geering
K
K
Rossier
B C
BC
D000375:Aging / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology; D004625:Embryo, Nonmammalian / Q000378:metabolism* / Q000502:physiology; D005314:Embryonic and Fetal Development; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D009865:Oocytes / Q000378:metabolism / Q000502:physiology; D011061:Poly A / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D016914:Ribonuclease H; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism*; D014982:Xenopus laevis
D012333:RNA, Messenger; D011061:Poly A; D016914:Ribonuclease H; D000254:Sodium-Potassium-Exchanging ATPase