EXTREMELY STABLE TRANSCRIPTS MAY COMPENSATE FOR THE ELIMINATION OF THE GENE FERT-1 FROM ALL ASCARIS-LUMBRICOIDES SOMATIC-CELLS

The single-copy gene fert-1 becomes eliminated from all somatic cells during the process of chromatin diminution in Ascaris lumbricoides var . suum. By using Northern blot and in situ hybridization techniques, w e have analyzed its rather unusual expression pattern. Different splic ing and 3' end formation events generate in a developmentally regulate d manner various poly(A)(+) and poly(A)(-) fert-1 RNA species. The lac k of any significant open reading frame in most of its RNA products in dicates that fert-1 may function as structural RNA rather than encodin g a protein. Fert-1 transcripts are produced in the precursors of the gametes, but degraded at the time of meiosis and not passed on to the zygote. Embryonic transcription of fert-1 sets in as soon as the femal e nucleus has completed its meiosis. Our data thus demonstrate that th e Ascaris transcription apparatus is active prior to the general onset of zygotic transcription, which we think takes place in the four- to six-cell-stage embryos. Upon elimination of fert-1 gene from the somat ic cells, most of its transcripts disappear. Two short fert-1 RNA prod ucts, however, are stably maintained throughout development until the second larval stage, which is more than 1 month after the elimination of their coding sequences. Possible functions of fert-1 are discussed. (C) 1994 Academic Press, Inc.