Nuclear localization of a DNA-binding C-terminal domain from Balbiani ring coded secretory protein.
All known Balbiani ring (BR) genes in Chironomus tentans, coding for giant secretory proteins, the sp-I family, end with a short (110 codons) 3'-end exon which is highly conserved in evolution and is structurally unrelated to the sequences characterizing the core of these proteins. We find that the expressed product, the C-terminal domain, shows sequence-specific DNA binding and that it is likely to be absent in one of the sp-I components, sp-Ib, believed to be coded by the BR2.2 gene. Immunohistochemistry shows that material with reactivity towards antibody against the C-terminal domain is present in the nuclei, and specifically enriched in Balbiani ring 1 and 2. Western blotting of extracts from isolated nuclei demonstrates a component with the same antibody reactivity and of an apparent size somewhat larger than that of the domain. The possibility is discussed that the C-terminal part, which is part of the secretion when derived from some of the BR genes, might be cleaved off and function as a feedback signal to control BR gene activity when derived from the BR2.2 gene.
Botella
L
L
Department of Genetics, University of Lund, Sweden.
Grond
C
C
Saiga
H
H
Edström
J E
JE
D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000648:ultrastructure; D002683:Chironomidae / Q000502:physiology*; D002875:Chromosomes / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D004175:Diptera / Q000502:physiology*; D007124:Immunoenzyme Techniques; D008970:Molecular Weight; D009687:Nuclear Proteins / Q000502:physiology* / Q000648:ultrastructure; D011506:Proteins / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011506:Proteins