Chromatin-bound DNA polymerase from higher plants

Abstract

Chromatin-bound DNA polymerase has been extracted from pea (Pisum sativum L.) seedlings, and partially purified by solubilization from chromatin followed by chromatography on columns of either DEAE-cellulose or DEAE-Sephadex. The enzyme elutes from DEAE-cellulose as a single peak, but is fractionated into two peaks, CI and CII, by DEAE-Sephadex chromatography. If the enzyme is stored at-15°C for several days prior to chromatography, a third peak, CIII, derived from CII, is obtained. The polymerase is devoid of nuclease activity, and is relatively insensitive to N-ethyl-maleimide. These features, taken with the ion requirements and with data obtained from other plant species, lead to the suggestion that the chromatin-bound DNA polymerase of higher plants is similar to the DNA polymerase-β from vertebrates.

Plant DNA polymerases

“…The low molecular weight polymerase from wheat shares with its animal counterpart the resistance to aphidicolin, the sensitivity to dideoxyTTP and ethidium bromide, as well as a partial recognition of poly rA-oligo dT template. Other authors have described polymerases of the/3 type based on the dubious criteria of a strong affinity of the enzyme to chromatin (18,13). Some investigators have proposed that plants do not possess a low molecular weight DNA polymerase, since this kind of enzyme could not be detected in crude wheat extracts and in Vinca rosea (19,7).…”

Biochemical Aspects of Dna Replication With Particular Reference to Plants

“…No details of ionic requirements were reported for the endodeoxyribonuclease of Tradescantia, except insofar as the assays were carried out in the presence of KCl and MgC1, at pH 7-6 (Kligman & Takats, 1975). The DNA polymerase was assayed under the same conditions, and it seems possible that the assay was optimized for DNA polymerase, rather than for endonuclease (see Stevens, Bryant & Wyvill, 1978). The chromatin-bound deoxyribonuclease of pea (Jenns & Bryant, 1978) certainly does not need magnesium, but is stimulated three-fold by 8 m~ calcium.…”

A low molecular weight DNA polymerase from wheat embryos

“…The absence of a small polymerase in wheat and Vinca rosea, as assayed in crude extracts by sucrose gradient centrifugation, led to the idea that this kind of enzyme was restricted to animal cells [7,12]. An enzyme strictly similar to animal DNA polymerase fl or present in all developmental stages has not been described in plant cells, although the presence of a small DNA polymerase has been reported in partially purified extracts from sugar beet and pea [9,30,33], lily [23] and cauliflower [35]. Other authors have classified a plant DNA polymerase as a fl-like enzyme based on the strong affinity of this enzyme to plant chromatin [9,33] which is the case of the nuclear animal enzyme.…”