Spatial and temporal distribution of a Drosophila melanogaster embryonic variable nuclear antigen

A polyclonal antibody has been prepared that specifically recognises a nuclear protein antigen in Drosophila embryos. During development, the antigen appears initially to be uniformly distributed but by nuclear division cycle 10 is seen to accumulate in nuclei in a manner suggesting that it is destroyed or becomes modified upon transition from S- to M phase of the nuclear division cycle. This conclusion is supported by the observed disappearance of the antigen from the postblastoderm nuclei in a manner that reflects the pattern of the first asynchronous postblastoderm cell division and persistence in the polyploid nuclei of the amnioserosa that do not undergo further cell or nuclear division. In Western blot experiments, the antibody detects specifically a 105 kDa nuclear protein that probably corresponds to the antigen detected in embryos by immunocytochemical means.