Translesion transcription by RNA polymerase II is one of the basic mechanisms for cellular tolerance to DNA damage and the major source of transcription errors. We recently elucidated the mechanism (the A-rule) employed by RNA polymerase II for transcription through the abasic sites in DNA that represent the most common DNA lesions in eukaryotic cells. We also study mechanisms enabling yeast and mammalian RNA polymerase II to transcribe through oxidative DNA lesions such as 8-oxoguanine and 5-hydroxyuracil.