Fig. 1.

Transcriptional memory of GAL genes. When yeast cells are grown in media containing galactose, the GAL genes necessary for galactose metabolism are induced (1st induction). Transcriptional memory upon re-exposure to galactose after a short period growth in glucose media significantly increases the rate of activation (2nd induction). Chromatin regulators including SWI/SNF and Htz1, Nuclear pore complex, and Gal4 activator positively regulate transcriptional memory of GAL genes. Furthermore, the Gal1 metabolic enzyme and the Gal3 protein regulating the function of the Gal4 activator are specifically required for long-term memory of GAL genes. Several factors including ISWI chromatin remodeling complex, Set1 HMT, and Tup1 negatively affect GAL memory.