Read-through histone transcripts containing 3' adenylate tails are zygotically expressed in Xenopus embryos and undergo processing to mature transcripts when introduced into oocyte nuclei.
Messages encoding replication-dependent histone genes generally terminate with a stem-loop structure and lack polyadenylate tails. Adenylated histone transcripts were identified in Xenopus oocytes, though the role of the adenylate tracts is unknown. We report isolation of cDNAs from Xenopus embryos encoding histone mRNAs with 3' adenylate tracts. They also contain targets for stem-loop binding protein and U7 snRNA, which are required for histone RNA processing. One sequence is a read-through transcript containing a complete version of the downstream gene from the anti-parallel strand, similar to the RNAs from lampbrush loops of Notophthalmus oocytes. We injected read-through transcripts into Xenopus oocyte nuclei and they were processed to mature histone RNAs. Our results suggest that addition of 3' adenylate sequences might be a normal part of histone RNA synthesis. Also, these results shed light on the enigma of the developmental regulation of adenylated histone transcripts in Xenopus oocytes.
Department of Pathology, College of Veterinary Medicine, University of Tennessee, 2407 River Drive, Knoxville, TN 37996-4500, USA.
Thomas
T
Masi
Andrew D
AD
Johnson
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D015723:Gene Library; D006657:Histones / Q000235:genetics* / Q000378:metabolism; D008845:Microinjections; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology*; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics
D006657:Histones; D012333:RNA, Messenger