PSF1 mutually regulates molecular stability of other GINS components. (A) Western blot analysis of GINS components ectopically expressed on NIH3T3 cells. Cells were cotransfected with VSVG-PSF2, HA-PSF3, and Myc-SLD5 in the presence (GINS) or absence (G-NS) of Flag-PSF1 or empty vector (Vector). The blots were probed with specific antibodies as indicated. GAPDH was used as a loading control. (B) Scheme of PSF1 expression in the course of HSC differentiation. The level of PSF1 expression is represented by the dark gray area. Both alleles of PSF1 are essential for populations in the light gray area.