Mitotic G2 Delay Induced in Synchronized Human Kidney Cells by Uv and X‐irradiation and Its Relation to Dna Strand Breakage, Repair and Transcription

Synchronous populations of human kidney T‐cells have been used to investigate the influence of BUdR incorporation into nuclear DNA on mitotic G2 delay produced by UV or X‐irradiation. By this means true G2 delay could be distinguished from a prolongation of the S‐phase. X‐ray induced mitotic delay is only slightly increased in BUdR containing cells. UV induced mitotic delay is appreciably augmented in cells having incorporated BUdR. These cells show extensive single‐strand breaks in their DNA which is fairly rapidly repaired. Transcription and translation are also appreciably reduced following UV in such cells. It is concluded that mitotic inhibition following X‐irradiation is a result of mechanisms other than the damage to and repair of DNA while mitotic inhibition following UV‐irradiation is primarily related to DNA damage and repair. The specific division proteins synthesized in G2 in these cells constitute only a minor component of the total soluble cell proteins.