In:
European Journal of Biochemistry, Wiley, Vol. 226, No. 1 ( 1994-11), p. 23-30
Abstract:
Analyses of cleavage ends of DNA fragments in apoptotic rat thymocytes induced by γ‐ray irradiation or by treatment with dexamethasone revealed that in both cases the fragments produced had 3′‐hydroxyl (OH) and 5′‐phosphoryl ( P ) ends of DNA chains. Rat thymocyte nuclei contained at least three endonuclease activities (deoxyribonucleases α, β and γ) that were able to cleave chromatin to mononucleosomal and oligonucleosomal fragments. The nuclei of apoptotic rat thymocytes induced by γ‐ray irradiation or dexamethasone retained considerable deoxyribonuclease γ activity, but not α or β deoxyribonuclease activity. During the induction of apoptosis, treatment with cycloheximide, which suppressed apoptosis, resulted in marked decreases of deoxyribonucleases α and β activities. After release of cycloheximide inhibition, DNA fragmentation associated with apoptosis occurred in the cycloheximide‐treated thymocyte nuclei, in which deoxyribonuclease γ activity was only observed. The purified deoxyribonucleases α and β were divalent cation‐independent acidic endonucleases, which were separated on a CM5PW column by HPLC. The molecular masses of deoxyribonucleases α and β were 28 kDa and 30 kDa, respectively, as determined by TSK G‐2000SW gel‐filtration HPLC, and both were 32 kDa in molecular mass as determined by SDS/PAGE. In contrast, deoxyribonuclease γ, a neutral endonuclease, required both Ca 2+ and Mg 2+ for full activity and was inhibited by Zn 2+ . The molecular mass of deoxyribonuclease γ was 31 kDa and 33 kDa when measured by gel filtration and SDS/PAGE, respectively. Under these optimal conditions, deoxyribonuclease γ was shown to produce 3′‐OH/5′‐ P ends of nucleosomal DNA fragments, while deoxyribonucleases α and β both formed DNA fragments with 3′‐ P /5′‐OH ends. The ends formed by cleavage with deoxyribonuclease γ were the same as those produced in apoptotic rat thymocytes. On the basis of these results, it seems likely that deoxyribonuclease γ is responsible for internucleosomal cleavage of chromatin during thymic apoptosis.
Type of Medium:
Online Resource
ISSN:
0014-2956
,
1432-1033
DOI:
10.1111/ejb.1994.226.issue-1
DOI:
10.1111/j.1432-1033.1994.00t23.x
Language:
English
Publisher:
Wiley
Publication Date:
1994
detail.hit.zdb_id:
1398347-7
detail.hit.zdb_id:
1464377-7
SSG:
12
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