Figure 4.

abp1⁺ and abp2⁺ function downstream of SPBC2A9.02 and SPAC27D7.08c to initiate DNA replication. (A) Reduced expression levels of abp1⁺ and abp2⁺ in SPBC2A9.02Δ and SPAC27D7.08cΔ. The mRNA levels were quantified by real time PCR and those of act1⁺ served as an internal control (n=3). The relative level in WT was designated as arbitrary unit 1. (B) Overexpression of abp1⁺ and abp2⁺ partially rescued the growth defect of SPBC2A9.02Δ and SPAC27D7.08cΔ. pREP1-abp1⁺ or pREP1-abp2⁺ were transformed into each deletion separately. pREP1-abp1⁺ and pJR2-41U-abp2⁺ were co-transformed into SPBC2A9.02Δ or SPAC27D7.08cΔ. Transformants were harvested and 5-fold serial dilutions were spotted on plates supplemented with DNA damage reagents. Plates were photographed after 3 days of incubation at 32°C. (C) Overexpression of abp1⁺ or abp2⁺ partially relieved the G1-arrest in SPBC2A9.02Δ and SPAC27D7.08cΔ. Transformants described in Figure 4B were grown to logarithmic phase and harvested for flow cytometry analysis. Reproducible results were obtained in three independent experiments.