Both Protection of Telomeres 1 proteins POT1a and POT1b can repress ATR signaling by RPA exclusion but binding to CST limits ATR repression by POT1b — ATR repression by POT1a and POT1b — Protection of telomeres 1 proteins POT1a and POT1b can repress ATR signaling by RPA exclusion, but binding to CST limits ATR repression by POT1b — ATR repression by POT1a and POT1b