Characterisation of the DNA-polymerase-alpha-primase complex from the silk glands of Bombyx mori.


Silk gland cells of Bombyx mori undergo chromosomal endoduplication ...
Silk gland cells of Bombyx mori undergo chromosomal endoduplication throughout larval development. The DNA content of both posterior and middle silk gland nuclei increased by 300,000 times the haploid genomic content, amounting to 18 rounds of replication. The DNA doubling time is approximately 48 h and 24 h during the fourth and fifth instars of larval development. However, DNA content does not change during the interim moult. Concomitant with DNA content, DNA polymerase activity also increases as development progressed. Enzyme activity is predominantly due to DNA polymerase alpha with no detectable level of polymerase beta. DNA polymerase alpha from silk gland extracts was purified to homogeneity (using a series of columns involving ion-exchange, gel-filtration and affinity chromatography), resulting in a 4000-fold increase in specific activity. The enzyme is a heterogeneous multimer of high molecular mass, and the catalytic (polymerase) activity is resident in the 180-kDa subunit. The enzyme shows a pI of 6.2 and the Km values for the dNTP vary over 5-16 microM. The polymerase is tightly associated with primase activity and initiates primer synthesis in the presence of ribonucleoside triphosphates on a single-stranded DNA template. The primase activity is resident in the 45-kDa subunit. The enzyme is devoid of any detectable exonuclease activity. The abundance of DNA polymerase alpha in silk glands and its strong association with the nuclear matrix suggest a role in the DNA endoduplication process.




new topics/pols set partial results complete validated


No results available for this paper.

Entry validated by:

Using Polbase tables:


Tables may be sorted by clicking on any of the column titles. A second click reverses the sort order. <Ctrl> + click on the column titles to sort by more than one column (e.g. family then name).


It is also possible to filter the table by typing into the search box above the table. This will instantly hide lines from the table that do not contain your search text.