Transient expression of RAD 51 in the late G2‐phase is required for cell cycle progression in synchronous P hysarum cells

The homologous recombination factor RAD 51 is highly conserved. This criterion enabled us to identify a RAD 51 ortholog in P hysarum polycephalum . We found that the P hysarum protein presents a high homology to the human protein and cross‐reacted with antibodies directed against the human RAD 51. Taking advantage of the natural synchrony of millions of nuclei within a single cell of Physarum , we investigated the fluctuation of the amount of the Pp RAD 51 throughout the cell cycle. Our results showed that in the late G2‐phase, RAD 51 was transiently expressed in a large quantity. Furthermore, knocking‐down RAD 51 in the G2‐phase abolished this transient expression before mitosis and affected cell cycle progression. These results support the idea that RAD 51 plays a role in the progression of the cell cycle in the late G2‐phase.