Nucleic Acids Research, 1986, Vol. 14, No. 2 703-719
© 1986
Articles |
A BR 1 gene in Chironomus tentans has a composite structure: a large repetitive core block is separated from a short unrelated 3'-terminal domain by a small intron
Department of Medical Cell Genetics, Karolinska Institute 104 01 Stockholm, Sweden
*To whom correspondence should be sent
Received November 1, 1985. Accepted December 3, 1985.
The large Balbiani ring ( BR ) genes in the dipteran genus Chironomus have been considered to be homogenous repetitive structures. Analysis of a genomic DNA segment now reveals that a BR 1 gene in C. tentans is a composite gene, consisting of two different types of sequences. A 15–20 kb core block of tandemly arranged repeat units extends close to the 3'end of the BR 1 gene and ends in repetitive structures partly different from the repeat units 1n the core block. A 55 bp long intron separates the core block, which probably constitutes a single exon, from a non-related 3'-exon, comprising the final 332 bp of the translated part of the gene.
According to hydrophobicity and secondary structure predictions, the 3'-exon encoded peptide is distinctly different from the repetitive core block domain and attains a globular structure. The carboxyl-terminal peptide domain is likely to be a general feature of BR encoded proteins and may have important functions in the excretion and polymerisation of the secretory proteins.
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