The tra-1 gene of Caenorhabditis elegans is a major developmental regulator that promotes female development. Two mRNAs are expressed from the tra-1 locus as a result of alternative mRNA processing. One mRNA encodes a protein with five zinc fingers and the other a protein with only the first two zinc fingers. We have derived a preferred in vitro DNA binding site for the five finger protein by selection from random oligonucleotldes. The two finger protein does not bind to DNA in vitro. Moreover, removal of the first two fingers from the five finger protein does not eliminate binding and has little effect on its preferred binding site. We find that a protein sequence amino-terminal to the finger domain also appears to play a role in DNA binding.
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We thank Jan Fogg and Terry Smith for synthesizing oligonucleotides and Mair Churchill, Mario de Bono and Richard Treisman for providing oligonucleotides and plasmids. We thank many colleagues at the MRC LMB for valuable discussions. We are grateful to Vivian Bardwell, Mario de Bono, Mark Bretscher, Andrew Travers and Richard Treisman for critical reading of the manuscript. D.Z. was supported by postdoctoral fellowships from the Helen Hay Whitney Foundation and the American Cancer Society. J.H. is an International Research Scholar of the Howard Hughes Medical Institute.