Absence of Replication fork associated factor CTF4 and F-box motif Encoding Gene SAF1 leads to reduction in Cell Size and Stress Tolerance Phenotype in S. cerevisiae

Chromosome transmission fidelity factor, Ctf4 in S. cerevisiae associates with replication fork and helps in the sister chromatid cohesion. At the replication fork, Ctf4 links DNA helicase with the DNA polymerase. The absence of Ctf4 invokes replication checkpoint in the cells. The Saf1 of S.cerevisiae interacts with Skp1 of SCF-E3 ligase though F box-motif and ubiquitinates the adenine deaminase Aah1 during phase transition due to nutrient stress. The genetic interaction between the CTF4 and SAF1 has not been studied. Here we report genetic interaction between CTF4 and SAF1 which impacts the growth fitness and response to stress. The single and double gene deletions of SAF1 and CTF4 were constructed in the BY4741 genetic background. The strains were tested for growth on rich media and media containing stress causing agents. The saf1{Delta}ctf4{Delta} cells with reduced cell size showed the fastest growth phenotype on YPD medium when compared with the saf1{Delta}, ctf4{Delta}, and WT. The saf1{Delta}ctf4{Delta} cells also showed the tolerance to MMS, NaCl, Glycerol, SDS, Calcofluor white, H2O2, DMSO, Benomyl, and Nocodazole when compared with the saf1{Delta}, ctf4{Delta}, and WT cells. However, saf1{Delta}ctf4{Delta} cells showed the sensitivity to HU when compared with WT and saf1{Delta}. Based on these observations we suggest that SAF1 and CTF4 interact genetically to regulate the cell size, growth and stress response.