HeLa cells were grown in F12:DMEM 50:50 (Hyclone) with 10% FBS, 2mM L-glutamine and antibiotics in 5% CO2 at 37 °C. Cells were synchronized in G1/S by treatment with 2 mM thymidine (Sigma-Aldrich) for 18-hours. The following siRNAs were used for siRNA transfections: ThermoFisher Silencer Select 4390843 (control non-targeting siRNA) and S9187 and S9188 (M1 and M2 siRNAs targeting MYL5); Dharmacon ON-TARGETplus D-001810-10 (control non-targeting siRNA) and J-011739-03 and J-011739-04 (M3 and M4 siRNAs targeting MYL5) were used as described previously (Torres et al. 2010 (link)). See Table S1 for a list of key reagents and resources used in this study and their pertinent information.