RAPADILINO RECQL4 mutant protein lacks helicase and ATPase activity

► RAPADILINO syndrome is associated with mutations in RECQL4. ► We characterize RAPADILINO RECQL4's catalytic activities relative to WT RECQL4. ► We show that RAPADILINO RECQL4 lacks helicase and ssDNA-dependent ATPase activity. ► RAPADILINO and RTS patients may develop cancer due to loss of helicase activity.