RT Journal Article SR Electronic(1) A1 Moore, Paul A. A1 Bettany, Andrew J. E. A1 Brown, Alistair J. P.YR 1990 T1 Multiple copies of the pyruvate kinase gene affect yeast cell growth JF Microbiology, VO 136 IS 12 SP 2359 OP 2366 DO https://doi.org/10.1099/00221287-136-12-2359 PB Microbiology Society, SN 1465-2080, AB The Saccharomyces cerevisiae pyruvate kinase gene (PYK1) was transformed into yeast using the multicopy vector pJDB207. Growth rates and PYK1 gene expression levels varied considerably amongst the transformants. Yeast transformants expressing the PYK1 gene at high levels formed small colonies compared with those expressing the gene at relatively low levels. Slow-growing transformants reverted at high frequency to more rapid growth, and this correlated with decreases in PYK1 gene copy number and PYK1 mRNA abundance. This apparent selection against PYK1 over-expression was disrupted by the introduction of a stop codon at the 5′-end of the PYK1 coding region, thus confirming that the growth effects were mediated by the PYK1 gene. However, massive overproduction of pyruvate kinase in yeast, using multiple copies of a PGK:PYK gene fusion, had no significant effect upon cell growth. This suggests that the deleterious effect upon the host yeast cell is mediated by abnormally high levels of the wild-type gene or PYK1 mRNA, rather than by increased pyruvate kinase levels., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-136-12-2359