Discontinuous synthesis of mRNA in trypanosomes.
Many trypanosome mRNAs have the same sequence of 35 nucleotides at their 5' end, encoded by a mini-exon located in 1.35-kb tandemly linked repeats. We have analysed nascent and steady-state mini-exon transcripts to determine how the mini-exon sequence is joined to the main part of trypanosome mRNAs. We show here that steady-state RNA from Trypanosoma brucei contains a transcript of 141 nucleotides that starts at the 5' border of the mini-exon. Isolated nuclei transcribe the segment corresponding to the 141 nucleotide RNA at a high rate; transcription of other areas of the 1.35-kb mini-exon repeat is approximately 750-fold lower. We propose that transcription of protein-coding genes in trypanosomes is discontinuous and involves the 141-nucleotide transcript as an intermediate.
D000818:Animals; D001483:Base Sequence; D004262:DNA Restriction Enzymes / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific; D005796:Genes; D012333:RNA, Messenger / Q000096:biosynthesis*; D012091:Repetitive Sequences, Nucleic Acid; D014158:Transcription, Genetic; D014345:Trypanosoma / Q000235:genetics*
D012333:RNA, Messenger; D004262:DNA Restriction Enzymes; C028649:endodeoxyribonuclease XmnI; D015252:Deoxyribonucleases, Type II Site-Specific