Disease relevance of CDC8

• The gene is shown to be nonessential for the replication of vaccinia virus in cultured cells by the construction of a viable virus mutant that has the coding region of the TmpK gene interrupted by the Ecogpt gene [1].
• Cell extracts of E. coli expressing the vaccinia gene contained high levels of TmpK activity, whereas extracts of cells without the TmpK gene did not [1].

High impact information on CDC8

• Replication in vitro mimics that in vivo in that DNA synthesis in extracts of strain cdc8, a temperature-sensitive DNA replication mutant, is thermolabile relative to the wild-type, and in that aphidicolin inhibits replication in vitro [2].
• Since the temperature-sensitive mutations are recessive, the products of genes cdc8 and cdc21 must be required for both nuclear and mitochondrial DNA replication [3].
• Yeast 2-microns plasmid DNA replication in vitro: purification of the CDC8 gene product by complementation assay [4].
• Seven of them fall into three complementation groups--cdc2, cdc8, and cdc16--involved in the control of the cell-division cycle [5].
• Extracts prepared from the cell division cycle mutants cdc7 and cdc8, held in culture at the nonpermissive temperature, possessed diminished activity [6].

Chemical compound and disease context of CDC8

• This hypothesis was tested, and as postulated, E. coli TmpK phosphorylates AZT-MP only 2.5 times slower than dTMP [7].
• This suggested that, if such a P-loop movement were to occur in the E. coli TmpK upon AZT-MP binding, it should not have such a detrimental effect on catalysis [7].
• TmpK from Escherichia coli lacks this arginine in its P-loop while having basic residues in the LID region [7].

Biological context of CDC8

• Unlike CDC8, the mRNA level of the URA6 gene did not fluctuate throughout the cell cycle; presumably, the temporal order of these two enzymatic activities might be different during cell cycle progression [8].
• In cdc8 and cdc21, mutants defective in continued replication during the S phase of the cell cycle, mitochondrial DNA replication ceases at the nonpermissive temperature [3].
• Thus the reading frame identified represents the authentic CDC8 gene, and the amino acid sequence of its product has been deduced [9].
• Third, the DNA sequence of the CDC8 gene reveals an open reading frame that encodes a protein with the same amino-terminal sequence as purified thymidylate kinase [10].
• We have sequenced a 42,500 bp stretch located on chromosome X of Saccharomyces cerevisiae between the genes MET3 and CDC8 [11].

Anatomical context of CDC8

• Subcellular fractionation indicates that thymidylate kinase is found in the combined nuclear and cytoplasmic fraction but not in the mitochondria [12].
• Similarly, DNA synthesis is reversibly temperature-sensitive in spheroplasts created from cdc7 and cdc8 mutant cells [13].

Associations of CDC8 with chemical compounds

• The CDC8 gene of Saccharomyces cerevisiae encodes deoxythymidylate (dTMP) kinase and is required for nuclear and mitochondrial DNA replication in both the mitotic and meiotic cell cycles [14].
• Unlike histone H2A mRNA, the CDC6 mRNA as well as CDC8 mRNA were not affected by hydroxyurea treatment [15].
• The structures of TmpK with dTMP and with AZT-MP [Lavie, A., et al. (1997) Nat. Struct. Biol. 4, 601-604] implicate the movement of Arg15 in response to AZT-MP binding as an important factor in the 200-fold reduced catalytic rate with AZT-MP [7].
• We propose that the resultant lysine to glutamate change stabilizes thermo-labile dTMP kinase molecules in the cell [14].
• The interactions of TmpK and TP5A strongly suggest that arginine 15, which is located in the phosphate binding loop (P-loop) sequence, plays a catalytic role by interacting with an oxygen atom of the transferred phosphoryl group [7].

Regulatory relationships of CDC8

• The CDC8 transcript is cell cycle regulated in yeast and is expressed coordinately with CDC9 and CDC21 at a point preceding histone transcription [16].
• The SOE1 mutant contains a dominant suppressor that suppresses five different cdc8 alleles but does not suppress a complete cdc8 deletion [14].
• The u.v.-sensitive rad4 mutant of yeast was found to decrease u.v.-induced reversion in the cdc8 and lys2 loci [17].

Other interactions of CDC8

• The accumulation of CDC9 mRNA in late G1 is dependent upon the completion of start but not the CDC7 and CDC8 functions [18].
• These data may explain an incomplete suppression of cdc8 by URA6, as previously observed [8].
• POL1 (DNA polymerase I) and CDC8 (thymidylate kinase) transcription were unaltered, while histone H2B transcripts actually decreased by half [19].
• This is precisely the same interval of the cell cycle in which three other yeast DNA synthesis genes, CDC8, CDC9 and CDC21, have been found to be periodically expressed (White et al 1987. Expl. Cell. Res., in press) [20].
• This fragment lies 1 kilobase downstream from the well-characterized sup4 gene, a gene known to be genetically linked to CDC8, thus confirming that the cloned gene corresponds to the chromosomal CDC8 gene [21].

References