[Cloning of BRCA1 cDNA and detection of BRCA1 mRNA expression in breast cancer cells].

The fragment of BRCA1 cDNA obtained by reverse transcription and polymerase chain reaction(RT-PCR) was inserted into plasmid pUC118 and demonstrated by DNA sequencing. Nucleotide sequence analysis demonstrated that the cloned cDNA for BRCA1 includes zinc finger domain. Two differences in nucleotides were found as compared with the sequence published. One occurs at nucleotide number 409 where Creplaced by A (Asp-->Glu). Another difference occurs at nucleotide number 879 where A replaced by T (samesense mutation). In order to further study the relationship-between BRCA1 function and breast cancer, the probe was prepared from the recombinant plasmid and then hybridized to total RNAs from 6 cases of breast cancer. Compared with normal cells, the expression level of BRCA1 mRNA was normal in 4, decreased markedly in 1, and in one patient there was no any expression of BRCA1 mRNA at all. The results suggested that the expression of BRCA1 mRNA was relatively low in some breast cancer cells.