Binding of human mitochondrial transcription factor A, an HMG box protein,to a four-way DNA junction

Mitochondrial transcription factor A (mtTFA), the only known transcription factor in mitochondria, is also implicated in maintenance of mitochondrial genome although little is elucidated about its molecular basis. mtTFA is a member of HMG box proteins family. Some HMG proteins bind with high affinit y to four-way DNA junctions that mimic a Holliday structure, a putative int ermediate in DNA recombination. To explore possible involvement of a Hollid ay-like structure in the maintenance of mitochondrial genome, we examine th e binding of recombinant human mtTFA to a synthetic four-way DNA junction. The human mtTFA binds to the four-may DNA junction with an approximately 10 -fold higher affinity than to the corresponding linear duplex DNA and with essentially the same affinity as to a 40-mer DNA containing the human mitoc hondrial Light strand promoter sequence. The mtTFA binds to the four-way as a monomer. Both of the two HMG box domains of human mtTFA are required for the high affinity binding to the four-way junction. (C) 2000 Academic Pres s.