Cosolvents facilitate DNA synthesis in the herpes simplex virus 1 unique short (Us) inverted repeat

DNA synthesis under standard conditions is not successful within a portion of the Us1 gene of HSV-1 which is juxtaposed to an 86% G + C-containing tract in the Us inverted repeat sequence. We report that the independent addition of specific amounts of at least three different types of cosolvents is capable of facilitating DNA synthesis within this G + C-rich region. In addition, this strategy was used to successfully place a specific site-directed mutation in the Us1 gene. Consideration of these observations should enable future site-specific mutational analyses of portions of the HSV-1 genome which have traditionally been unamenable to genetic manipulations.