Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA-binding protein HD with a monomer molecular weight of 9000 was isolated from Escherichia coli cells. The protein occurs as a tetramer under native conditions and binds to single and double-stranded DNA and also to RNA. DNA complexed with protein HD is a poor template for DNA synthesis by E. coli polymerase I, II or III holoenzyme. Exonuclease III is hindered in degrading HD-protein-covered double-stranded DNA, whereas exonuclease I can digest complexed single-stranded DNA. Transcription is liqhtly stimulated in the presence of protein HD.
 ...
PMID:Interaction of DNA with DNA-binding proteins. The characterization of protein HD from Escherichia coli and its nucleic acid complexes. 1 66

The major abasic endonuclease of human cells, Ape1 protein, is a multifunctional enzyme with critical roles in base excision repair (BER) of DNA. In addition to its primary activity as an apurinic/apyrimidinic endonuclease in BER, Ape1 also possesses 3'-phosphodiesterase, 3'-phosphatase, and 3'-->5'-exonuclease functions specific for the 3' termini of internal nicks and gaps in DNA. The exonuclease activity is enhanced at 3' mismatches, which suggests a possible role in BER for Ape1 as a proofreading activity for the relatively inaccurate DNA polymerase beta. To elucidate this role more precisely, we investigated the ability of Ape1 to degrade DNA substrates that mimic BER intermediates. We found that the Ape1 exonuclease is active at both mismatched and correctly matched 3' termini, with preference for mismatches. In our hands, the exonuclease activity of Ape1 was more active at one-nucleotide gaps than at nicks in DNA, even though the latter should represent the product of repair synthesis by polymerase beta. However, the exonuclease activity was inhibited by the presence of nearby 5'-incised abasic residues, which result from the apurinic/apyrimidinic endonuclease activity of Ape1. The same was true for the recently described exonuclease activity of Escherichia coli endonuclease IV. Exonuclease III, the E. coli homolog of Ape1, did not discriminate among the different substrates. Removal of the 5' abasic residue by polymerase beta alleviated the inhibition of the Ape1 exonuclease activity. These results suggest roles for the Ape1 exonuclease during BER after both DNA repair synthesis and excision of the abasic deoxyribose-5-phosphate by polymerase beta.
 ...
PMID:Modulation of the 3'-->5'-exonuclease activity of human apurinic endonuclease (Ape1) by its 5'-incised Abasic DNA product. 1285 37