GTBP, A 160-KILODALTON PROTEIN ESSENTIAL FOR MISMATCH-BINDING ACTIVITY IN HUMAN-CELLS

DNA mismatch recognition and binding in human cells has been thought t o be mediated by the hMSH2 protein. Here it is shown that the mismatch -binding factor consists of two distinct proteins, the 100-kilodalton hMSH2 and a 160-kilodalton polypeptide, GTBP (for G/T binding protein) . Sequence analysis identified GTBP as a new member of the MutS homolo g family. Both proteins are required for mismatch-specific binding, a result consistent with the finding that tumor-derived cell lines devoi d of either protein are also devoid of mismatch-binding activity.