THE CORRECTED NUCLEOTIDE-SEQUENCES OF THE TAQI RESTRICTION AND MODIFICATION ENZYMES REVEAL A 13-CODON OVERLAP

The nucleotide sequence of the genes encoding methyltransferase TaqI ( M.TaqI) and restriction endonuclease TaqI (R.TaqI) with the recognitio n sequence, TCGA, were analyzed in clones isolated from independent li braries. The genes, originally reported as 363 and 236 codons long [Sl atko et al., Nucleic Acids Res. 15 (1987) 9781-9796] were redetermined as 421 and 263 codons long, respectively. The C terminus of the taqIM gene overlaps the N terminus of the taqIR gene by 13 codons, as obser ved with the isoschizomeric TthHB8I restriction-modification system [B arany et al., Gene 112 (1992) 13-20]. Removal of the overlapping codon s did not interfere with in vivo M.TaqI activity. We postulate the ove rlap plays a role in regulating taqIR expression.