Structure of the Drosophila DNA topoisomerase I gene and expression of messages with different lengths in the 3' untranslated region.
The nucleotide sequence of the Drosophila DNA topoisomerase I gene (top1) has been determined. Structurally, top1 consists of eight exons and seven introns. The top1 coding region contains a new class of opa repeats, encoding clusters of serine residues instead of glutamine repeats usually seen in Drosophila genes of the neurogenic loci. A unique feature of top1 is the developmental switch of its transcripts: a heterogeneous population of transcripts ranging from 3.8 to 4.2kb seen maximally at 0-2h of embryogenesis and a 5.2-kb transcript maximal at 6-12h of embryonic development. The transcripts expressed in the 0-2-h embryo have been shown as maternal storage products specific to ovarian tissues. RACE analysis shows that whereas the 6-12-h transcripts have a single site for polyadenylation, there are at least 12 different sites for poly(A) addition to the 0-2-h transcripts. An additional intron specific for the maternal storage transcripts appears in some of the 0-2-h transcripts. No significant heterogeneity at the 5' end of the top1 transcripts is seen. Sequence searches have revealed a number of regulatory sequences for potential translational control in the 3' untranslated region.
Brown
S D
SD
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Zhang
C X
CX
Chen
A D
AD
Hsieh
T S
TS
D000818:Animals; D001483:Base Sequence; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D004330:Drosophila / Q000737:chemistry / Q000201:enzymology / Q000235:genetics*; D005091:Exons / Q000235:genetics; D005260:Female; D015870:Gene Expression / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D017344:Genes, Insect / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008297:Male; D009928:Organ Specificity; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic / Q000235:genetics
D012333:RNA, Messenger; D004264:DNA Topoisomerases, Type I