fcsA29 mutation is an allele of polA gene of Escherichia coli

The cold-sensitive fcsA29 mutation of Escherichia coli was found to be a ne w type of cold-sensitive allele of the polA gene encoding DNA polymerase I, caused by an Asp(116)-->Asn change in the 5'-->3' exonuclease domain. The fcsA29 mutant showed typical polA mutant phenotypes such as UV sensitivity and unacceptability of recA mutation. Cold-sensitive growth of the mutant w as suppressed by introduction of a sulA mutation, indicating that cell fila mentation was due to the SOS response.