This is problematic for the efficient isolation of rAAV from keratinized PT3 cells. However this possibility is worth investigating. Niet aland Nashet al[41,42] identified POLD1 as the central DNA polymerase, which is a leading
strand DNA polymerase, the main mechanism through which AAV DNA replication takes place. The need of PCNA and RFC is also compatible with POLD1 as the main AAV-polymerase as PCNA is the processivity factor for POLD1, and RFC is known to assemble PCNA onto 3′OH primers. RPA was not found essential when using adenovirus-infected cell extracts, in contrast to uninfected cell extracts . In any case these data are also consistent with Christensen and Tattersall  who found that these same four proteins (POLD1, 17DMAG in vivo RPA, PCNA, and RFC) were the minimum cellular factors required for MVM DNA rolling-circle replication when using a 3′-dimer junction. However theirin vitroreactions C188-9 in vivo also included MVM NS1 protein and cellular PIF protein. In the latest study by Nashet al it was mentioned that there is one additional protein component (present in P-Cell IA) which was needed but was unidentified. It was further speculated that it was a cellular helicase. To approach this question we revisited the PT3vsPT1/NK DNA microarray data to observe if particular DNA helicases or overall helicase activity was higher in PT3.
This approach seems valid as even though we have not done the usual triple-DNA microarray analysis, the real-time quantitative PCR expression data fully confirmed the DNA microarray results across multiple genes. Thus, the Affymetrix microarray data we have in hand appears worthy of study for gleaning suggestive information on the AAV-permissive transcriptome. It was found, as shown in Table2, that the overall helicase activity was not significantly different in PT3 cells, with two helicases being up-regulated and one down-regulated in PT3 versus NK/PT1. While POLD1 was clearly found required for AAVin SCH772984 in vitro vitroreplication by Nash et al  there is a possibility the DNA
Polymerase alpha might be involved in certain “”alternative”" forms of AAV DNA replication, such as through the use of http://www.selleck.co.jp/products/MDV3100.html internal origins of replication . Both SV40 and parvovirus H-1 are able to use Polymerase alpha for replication [46,47]. To approach this question we revisited the PT3vsPT1/NK DNA microarray data to observe if DNA polymerase alpha was higher in PT3. The results of the Affymetrix data are shown in Table3, and suggest that DNA polymerase alpha is also significantly up-regulated in PT3 over PT1 and NK. However, the importance of this up-regulation, if any, is not yet determined. One question which arises from this data is how or if the four components are coordinately up-regulated in PT3 cells.