Disease relevance of RAD27

• Saccharomyces cerevisiae RAD27 complements its Escherichia coli homolog in damage repair but not mutation avoidance [1].
• Several other replication mutations, such as rad27 Delta, encoding the FEN-1 nuclease involved in several aspects of genomic stability, also show premature aging [2].
• When the mutant enzyme E160D was expressed in yeast, it partially complements the biological functions of the homologous yeast gene, RAD27, and reverses the hyper-temperature lethality and hypersensitivity to methyl methanesulfonate, in a manner corresponding to the in vitro activity [3].
• Extensive work on the maturation of lagging strands during the replication of simian virus 40 DNA suggests that the initiator RNA primers of Okazaki fragments are removed by the combined action of two nucleases, RNase HI and Fen1, before the Okazaki fragments join [4].

High impact information on RAD27

• To clarify the molecular basis of FEN-1 specificity and PCNA activation, we report here structures of FEN-1:DNA and PCNA:FEN-1-peptide complexes, along with fluorescence resonance energy transfer (FRET) and mutational results [5].
• Structural basis for FEN-1 substrate specificity and PCNA-mediated activation in DNA replication and repair [5].
• Mutations in RAD27 cause increased rates of mitotic crossing over and are lethal in combination with mutations in RAD51 and RAD52 [6].
• Mutations in the S. cerevisiae RAD27 (also called RTH1 or YKL510) gene result in a strong mutator phenotype [6].
• The duplication mutations seen in rad27 mutants occur both in human tumors and as germline mutations in inherited human diseases [6].

Chemical compound and disease context of RAD27

• We found that the yeast Rad27 protein complements sensitivity to methyl methanesulfonate in an E. coli mutant [1].

Biological context of RAD27

• Mutations in RAD27 define a potential link between G1 cyclins and DNA replication [7].
• Deletion of RAD27 results in defective Okazaki fragment maturation, DNA repair, and subsequent defects in mutation avoidance and chromosomal stability [8].
• The 3'-->5' exonuclease of DNA polymerase delta can substitute for the 5' flap endonuclease Rad27/Fen1 in processing Okazaki fragments and preventing genome instability [9].
• We examined this prediction by analyzing the terminal DNA structures generated during telomere replication in rad27 strains [10].
• The lengths of the telomeric repeat tracts were found to be destabilized in rad27 strains, indicating that naturally occurring direct repeats are subject to tract expansions and contractions in such strains [10].

Anatomical context of RAD27

• The FEN1 nuclease functions during Okazaki fragment maturation in the eukaryotic cell [11].
• To determine the possible use of the enzymes in RNA structure analysis, the cleavage of synthetic and native RNAs was examined using flap endonuclease 1 (Fen1) of HeLa cells [12].

Associations of RAD27 with chemical compounds

• All four rad27 mutants showed similar high levels of mitotic recombination, but varied in their growth rate at various temperatures, and sensitivity to the DNA damaging agent methyl methane sulfonate [13].
• Genetic analysis of Saccharomyces cerevisiae also has identified a role for Rad27p in mutation avoidance. rad27Delta mutants display both a repeat tract instability phenotype and a high rate of forward mutations to canavanine resistance that result primarily from duplications of DNA sequences that are flanked by direct repeats [14].
• The rth1 delta mutation does not affect UV or gamma-ray sensitivity but enhances sensitivity to the alkylating agent methyl methanesulfonate [15].
• These results suggest that unprocessed DNA strand breaks at AP sites are mainly responsible for the MMS sensitivity of rad27 mutants [16].
• Base excision repair (BER) of uracil-containing DNA was deficient in rad27 mutant extracts in that (i) the Apn1 activity was reduced, and (ii) after DNA incision by Apn1, hydrolysis of 1-5 nucleotides 3' to the baseless sugar phosphate was deficient [16].

Physical interactions of RAD27

• Two modes of FEN1 binding to PCNA regulated by DNA [11].

Regulatory relationships of RAD27

• We show that overexpression of EXO1 suppresses multiple rad27 null mutation-associated phenotypes derived from DNA replication defects, including temperature sensitivity, Okazaki fragment accumulation, the rate of minichromosome loss, and an elevated mutation frequency [8].
• In agreement with these results, the proposed generation of double strand breaks in pol3-exo(-) rad27 mutants was suppressed by the overexpression of DNA2 [17].
• Suppression of the temperature-sensitive growth defect of dna2Delta405N required the presence of a functional copy of RAD27, indicating that Mgs1 suppressed the dna2Delta405N mutation by increasing the activity of yFen1 (Rad27) in vivo [18].

Other interactions of RAD27

• Overlapping functions of the Saccharomyces cerevisiae Mre11, Exo1 and Rad27 nucleases in DNA metabolism [19].
• Increased Exo1 or TLC1 RNA did not alter checkpoint responses or restore NHEJ proficiency, but DNA repair defects of yku70 and rad27 (fen) mutants were differentially suppressed by the two genes [20].
• RAD2, a homolog of RTH1, is required for nucleotide-excision repair [21].
• The in vivo role of the PCNA interaction was investigated in the yeast Rad27 [22].
• Overexpression of Dna2p in wild-type cells also yielded single-stranded DNA regions on telomeric DNA and caused a cell growth arrest phenotype virtually identical to that seen for rad27 cells grown at the restrictive temperature [10].

Analytical, diagnostic and therapeutic context of RAD27

• If FEN1 is absent or not optimally functional, the ability of Pol delta to back up via its 3'-5'-exonuclease activity, a process called idling, maintains the polymerase at a position that is ideal either for ligation (in case of a DNA-DNA nick) or for subsequent engagement by FEN1 (in case of a DNA-RNA nick) [23].
• To assess the roles of the active site residues Glu160 and Asp181 of human FEN-1 nuclease in binding and catalysis of the flap DNA substrate and in vivo biological processes of DNA damage and repair, five different amino acids were replaced at each site through site-directed mutagenesis of the FEN-1 gene [3].
• Peptide sequence analysis of the purified 47 kDa exonuclease was carried out, and the peptide sequence was found to be identical to the S. cerevisiae gene YKL510 encoded polypeptide, which is also known as yeast RAD2 homolog 1 or RTH1 nuclease [24].

References