Cell Cycle, Cell Size Regulation

Cell length growth patterns in fission yeast reveal a novel size control mechanism operating in late G2 phase

“…Weak size control means that the slope of the regression line for Ext versus L RCP1 is somewhere between −1 and 0, and L RCP3 is positively correlated to L RCP1 . If there is no negative correlation between Ext and L RCP1 , size control is lacking (see Sveiczer et al., ; Sveiczer and Rácz‐Mónus, for further details). For the strains studied here, a strong size control was found in WT, WT diploid, wee1Δ , cdc2˗3w cdc25Δ and cdc2˗3w cdc25Δ pyp3Δ cells (Ext vs. L RCP1 slopes between −0.622 and −1.318; Table ) in agreement with our previous findings (Sveiczer et al., ).…”

“…To maintain a characteristic cell size distribution during consecutive generations, unicellular organisms need to grow during their cell cycle in a controlled way. This requires a size regulation mechanism that coordinates growth and division (Sveiczer and Rácz‐Mónus, ; Alberts et al., ). The growth pattern during the cycle can be described by different mathematical functions.…”

“…It was assumed that the critical size threshold was reached just before mitotic onset in late G2 (Fantes and Nurse, ). Since the Wee1 kinase is an essential element of setting a size threshold for mitotic onset, size homeostasis cannot be maintained via this mechanism in the small wee1 − mutant lacking this activity (Sveiczer and Rácz‐Mónus, ). Another size control mechanism that sets a critical size for starting DNA replication was discovered to operate in these mutant cells (Nurse and Thuriaux, ).…”