Because S. pombe mms22 is indispensable for replication-associated DNA damage that is repaired by HR, and the mms22Δ/ rph57Δ double mutant displayed additive growth deficiencies and DNA damage sensitivites (Table 3) (Dovey and Russell 2007; Yokoyama et al. 2007), we investigated a similar interaction of CaMMS22 with the HR genes in C. albicans.
While the minimum length of T-stretch is not known, long T-stretches (>10 bp) seem to be indispensable for the replication initiation of mtDNA [ 28].
Interestingly, reverse gyrase, the enzyme, which is the genomic signature of hyperthermophiles [ 63] and is thought to be indispensable for DNA replication and transcription at extremely high temperatures [ 64], is part of the latter subset and belongs to LUCA1.0 under the rRNA tree topology but not under the genome-tree topology.
Both L1-encoded proteins appear to be indispensable for the proposed mechanism, and this implies that only those FL-L1 transcripts that are assembled with both proteins can function in terms of noncanonical replication.
Again, this will be indispensable for making any replacements.
Rescue experiments with various truncated dRecQ4 proteins suggest that the N-terminal domain of dRecQ4 is essential for DSB repair, whereas both the N-terminal domain and the helicase domain are indispensable for DNA replication and animal viability.
TS (thymidylate synthase) is a key enzyme in the de novo biosynthesis of dTMP, and is indispensable for DNA replication.
VP35 is a multifunctional major virulence protein that is indispensable for EBOV replication as a component of the viral polymerase complex.
This study demonstrated that the determinants rep165, ori165 and the iterons region are indispensable for plasmid replication; and that orf6 and orf10 are involved in stable maintenance of the plasmid.
As an aside, in higher eukaryotic cells, the Rad51 ortholog and other HR factors are indispensable for DNA replication, and the inactivation of genes encoding these proteins is lethal, whereas equivalent recombination proteins are dispensable for viability in both yeast species (reviewed in San Filippo, Sung and Klein 2008; Errico and Costanzo 2010).
