The 5'-flanking sequence of the loach oocyte 5S rRNA gene contains a signal for effective transcription.
Deletion mutants of loach oocyte 5S rRNA genes were injected and transcribed in vivo in the nuclei of loach (Misgurnus fossilis) and Xenopus laevis. A control region was found in the 5'-flanking sequence, the elimination of which greatly decreases in vivo transcription of 5S rRNA genes. This cis-acting element is located in the region between nt-18 and the transcription start point. We propose that the oocyte nucleus contains (a) specific transcriptional factor(s), NTFO, which interacts with the cis-acting element we described. We also propose that NTFO is inactivated in maturing oocytes when nucleoplasm interacts with oocyte cytoplasm after germinal vesicle breakdown. The residual activity of this factor(s) may be responsible for low-level synthesis of oocyte 5S rRNA at the beginning of embryogenesis. We consider the disappearance of NTFO during gastrulation to be responsible for the total inactivation of oocyte 5S rRNA genes in embryonic and somatic tissue.
W. Engelhardt Institute of Molecular Biology, USSR Academy of Sciences, Moscow.
P
P
Felgenhauer
J
J
Sedman
N
N
Shostak
M
M
Timofeeva
A
A
Lind
A
A
Bayev
D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D003531:Cypriniformes / Q000235:genetics*; D005775:Gastrula / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D012341:RNA, Ribosomal, 5S / Q000096:biosynthesis*; D012045:Regulatory Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic; D014981:Xenopus / Q000235:genetics*
D012335:RNA, Ribosomal; D012341:RNA, Ribosomal, 5S; D014157:Transcription Factors