CHEK2 and infection: Additionally, we noted that infection of LECs by KSHV-Lyt led to a marked increase in the levels of phosphorylated CHK2 at threonine 68 (pCHK2-T68) and p53 at serine 15 (pp53-S15) as early as 24 h p.i., marking the induction of the DNA damage response (DDR).