The transcription of one group of genes including rpb 3 , rpb 4 , rpb 5 , rpb 6 , rpb 7 and rpb 10 is mainly initiated at a single site , while that of the other group of genes for rpb 1 , rpb 2 , rpb 8 , rpb 9 , rpb 11 and rpb 12 is initiated at multiple sites . ^^^