Both were found to be essential for viability.
The molecular chaperone Hsp90 has been found to be essential for viability in all tested eukaryotes, from the budding yeast to Drosophila.
As budding yeast SPC97 and SPC98, fission yeast and Drosophila Alp4/GCP2 (the homologue Spc97) and Alp6/GCP3 (the homologue Spc98) were found to be essential for viability.
CK2α has been found to be essential for viability in all organisms in which its role has been assessed, including P. falciparum [ 19].
Despite their smaller number, however, the latter category was found to be more essential to viability, more highly expressed, and more connected to protein interaction networks [ 1].
The AN1959 gene is further studied and found to be essential for the viability of spores, thus named as vosA (see below).
In both prokaryotes and eukaryotes, members of the Omp85 family were found to be essential for cell viability.
Homologues of U1A, U2B″, and U2A′ have been found to be essential for the viability of Drosophila and Caenorhabditis elegans, and in both Drosophila and C. elegans, U2A′ has functions that are independent of snRNP.
Along with one other tail mutation that evolved later, they were even found to be collectively essential to the viability of the adapted T3Δ1.3AE.
Significantly, APE1 has been found to be essential for not only animal viability, but also for cell viability in culture [8], [9].
Interestingly, some point mutations in regions that are identical from yeast to humans were not found to be essential for cap methylation or yeast viability [ 31].
