Expression of the polyubiquitin-encoding gene ( ubq-1) in transgenic Caenorhabditis elegans

Abstract

The expression of the polyubiquitin-encoding gene ( ubq-1) of Caenorhabditis elegans was analysed using transgenic nematode lines carrying translational ubq-1::lacZ fusions. Animals carrying a construct consisting of 938 bp of ubq-1 upstream sequences fused to lacZ (ubq938::lacZ) expressed βGal in embryos and in a tissue-general manner in 20% of L1 larvae. Somatic expression in later stages was usually confined to body muscle. Progressively larger deletions extending from the 5′ end of ubq938:: lacZ did not significantly alter the pattern of expression until 827 bp of sequence had been removed. Thus, sequences upstream from the transcription start point, including a G+C-rich block and a sequence resembling a TATA box (GAATAA), are not required to generate the expression pattern seen with ubq938:: lacZ. Moreover, a basal level of expression was maintained in embryos when 903 bp were deleted. These results suggest that the promoter elements required for efficient expression of ubq-1 may reside within the transcribed region of the gene; alternatively, they must lie more than 1.7 kb upstream or 0.8 kb downstream from this region. Polymerase chain reaction analysis indicates that RNA molecules transcribed from the ubq938:: lacZ and ubq°827:: lacZ transgenes are trans-spliced to SL1, as is ubq-1 RNA.