Characterization of telomere-associated ARSs(autonomously replicating sequences) and their use for multiple gene integration in Hansenula polymorpha

Abstract

A yeast, Hansenula polymorpha is one of the promising hosts for the production of recombinant proteins due to the availability of powerful promoters and the possibility of multiple integration of a transforming DNA. To develop a multiple gene integration system in H. polymorpha strain DL-1, several autonomously replicating sequences of Hansenula(HARSs) with the characteristics of tandem integration were cloned by an enrichment procedure and characterized for their functional elements. All plasmids harboring newly cloned HARSs showed a high frequency of transformation and integration into the chromosome after stabilization. HARS36 was selected for its high efficiency of transformation and tendency of integration. Several tandemly repeated copies of the transforming plasmid containing HARS36 integrated into the vicinity of the chromosomal end. Three functional domains of HARS36, A, B and C, required for its HARS activity were analyzed by deletion analyses. Domain A contained AT-rich ARS core sequences. Domain B contained two directly repeated sequences, RS-I and RS-II which were predicted to form a bent DNA structure. Deletion of the AT-rich core in domain A resulted in a complete loss of ARS activity, and deletion of the bent region in domain B greatly reduced the stability of the transforming plasmid. Domain C included 18 identical repetitions of the direct repeat sequence(5``-GGGTGGCG-3``) which is required for the facilitated chromosomal integration of transforming plasmids. The chromosomal origin of HARS36 was found to be an end of a chromosome which contains a telomeric ARS(domains A and B) and telomeric repeated sequence(domain C). Genomic Southern blotting with a telomeric fragment of HARS36 as a probe showed several homologues in the genome which were sensitive to endonuclease Bal31. It indicated that HARS36 is a member of multiple ARSs, which are located near several telomeres of different chromosomes (HARS36 type). Several telomeres, if not all, were...