Expression of SPT4 is modulated negatively by PUF4 and positively by RAD2

초록

RAD2, a yeast homolog of human XPG gene, encodes nucleotide excision repair (NER) endonuclease that incises the 3' side od damaged DNA. Mutations of XPG causes human inherited genetic disorders, xeroderma pigmentosum and Cockayne syndrome depends on tha nature of the mutations. Previously we showed that RAD2 functions in transcription elongation and 6-Azauracil (6AU) sensitivity of rad2d can be complemented by deltion of puf4 that functions in transcription elongation. SPT4, a transcription elongation factor and a subunit of DSIF, is one of the gene of which expression was implied to be modulated by PUF4. Expression of SPT4 in rad2d in the presence of 6AU was decreased by 30% compared to that oin wildtyoe while it was increased by 165% and 252% in puf4d and rad2dpuf4d, respectively. In accordance with the SPT4 expression pattern, puf4d partially complements severe 6AU sensitivity of spt4d as it decreased 6AU sensitivity of rad2d. Interestingly, double deletion of rad2d and spt4d did not increase 6AU sensitivity of spt4d inicating that both genes might function in the same transcription elongation pathway. These results show that SPT4 expression is indeed modulated by PUF4 and also implied that RAD2 might to be involved in transcription elongation of SPT4.