Disease relevance of RpLP0

• The C-terminal portion of the predicted protein contained regions of presumptive DNA-binding domains, while the DNA sequence at the amino end of AP3 showed similarity to the Escherichia coli recA gene [1].
• Baculovirus apoptotic suppressor P49 is a substrate inhibitor of initiator caspases resistant to P35 in vivo [2].

High impact information on RpLP0

• The predicted Ape protein, which contains likely nuclear transport signals, is a member of a family of DNA repair enzymes that includes two bacterial AP endonucleases (ExoA protein of Streptococcus pneumoniae and exonuclease III of Escherichia coli) and Rrp1 protein of Drosophila melanogaster [3].
• Purified Ape protein lacks the 3'-exonuclease activity against undamaged DNA that is found in the bacterial and Drosophila enzymes, but the lack of obvious amino acid changes to account for this difference suggests that the various enzyme functions evolved by fine tuning a conserved active site [3].
• The cDNA clone yielded an in vitro translation product of 35,000 daltons, in agreement with the predicted size of the translation product of the only open reading frame of AP3, and identical to the molecular size of an AP endonuclease activity recovered following sodium dodecyl sulfate-polyacrylamide gel electrophoresis of Drosophila extracts [1].
• The 1.2-kilobase (kb) AP3 cDNA mapped to a region on the third chromosome where a number of mutagen-sensitive alleles were located [1].
• AP3 is expressed as an abundant 1.3-kb mRNA that is detected throughout the life cycle of Drosophila melanogaster [1].

Biological context of RpLP0

• This phosphorylation increases YA's binding to P0 [4].
• The cDNA of a Drosophila DNA repair gene, AP3, was cloned by screening an embryonic lambda gt11 expression library with an antibody that was originally prepared against a purified human apurinic-apyrimidinic (AP) endonuclease [1].
• In addition, l(3)01544 suppresses the variegated phenotypes of In(1)wm4h and In(1)y3P, suggesting a potential involvement of the P0 protein in modifying position effect variegation [5].
• Mutation in P0, a dual function ribosomal protein/apurinic/apyrimidinic endonuclease, modifies gene expression and position effect variegation in Drosophila [5].
• In a search for modifiers of gene expression with the white eye color gene as a target, a third chromosomal P-element insertion mutant l(3)01544 has been identified that exhibits a strong pigment increase in a white-apricot background [5].

Anatomical context of RpLP0

• Drosophila P0/AP3, a ribosomal protein that is also an apurinic/apyrimidinic endonuclease, binds to YA in ovary and embryo cytoplasms [4].
• We furthermore show that GST-PO can be located in both the nucleus and ribosomes [6].
• Its nuclear location can be further traced to the nuclear matrix, thus placing PO in a subcellular location where it could act as a DNA repair protein [6].
• The anti-apoptotic baculoviral P35 protein acts downstream of hid activity to suppress the photoreceptor cell death driven by rpr and hid [7].

Associations of RpLP0 with chemical compounds

• In support of this notion, tests were performed that show that GST-PO, but not GST, was able to rescue an E.coli mutant lacking the major 5'-acting AP endonucleases from sensitivity to an alkylating agent [6].

Enzymatic interactions of RpLP0

• We propose that the P0-containing 20S cytoplasmic complex retains hyperphosphorylated ovarian YA in the cytoplasm [4].

Other interactions of RpLP0

• P0 and YA bind specifically and directly in vitro and are present in a 20S complex in the cytoplasmic extracts [4].
• Biochemical tests were originally performed to see if overexpressed PO contained DNase activity similar to that recently reported for the apurinic/apyrimidinic (AP) lyase activity associated with Drosophila ribosomal protein S3 [6].
• Furthermore, pull-down and immunoprecipitation experiments suggest a direct interaction between Staufen 1 and the ribosomal protein P0 in vitro as well as in cells [8].

Analytical, diagnostic and therapeutic context of RpLP0

• Interestingly, the medfly CcP0 seems to be the only P0 protein of higher eukaryotic organisms with basic character (pI 8.5), as shown by electrofocusing of purified ribosomes [9].

References