Because 293A cells lack expression of SV40 large T antigen, the plasmid is replicated transiently using an alternative replication mode that initiates randomly throughout the plasmid (Chandok et al. 2011).
Ctf8 is part of an alternative replication factor C complex, whereas Chl1 is a replicative helicase; deletions were previously reported to be synthetically sick with cohesin mutants in S. cerevisiae (Costanzo et al. 2010).
Nevertheless, they might theoretically be ensured by alternative replication factors as those encoded, for example, by prophages.
DSCC1 is a component of an alternative replication factor C complex that loads PCNA onto DNA during S phase.
We compared binding to OriP with a control region within the alternative replication initiation zone used in Raji cells, referred to as OriR [45].
We have previously shown that swi3Δ is synthetically lethal with deletion of ctf18, which encode the largest subunit of an alternative replication factor C complex (RFCCtf18) required for establishment of sister chromatid cohesion [37], [42], [43].
It is also discarded that the putative alternative replication factors are of chromosomal origin since B. subtilis does not encode structural and/or functional homologues of the DnaC helicase and DnaG primase that could replace efficiently these proteins at the fork [70].
As a more efficient alternative, replication-defective viral vectors have been developed to silence genes in tumours.
The beneficial effect of complementation may be enhanced by efficient mtDNA replication, as provided by CR mutations which introduce alternative replication sites.
The orc5 gene is located on the main chromosome in all three organisms and might play a role in alternative replication start sites under stress conditions.
Since the C150T transition is able to provide alternative replication origins [ 5], a similar effect could be hypothesized for the other mutations.
