pGF1-GAS-LUC, which expresses a puromycin selection cassette and firefly luciferase reporter under the control of a minimal cytomegalovirus promoter followed by four tandem consensus GAS elements (5′-AGTTTTCATATTACTCTAAATC-3′) was purchased from System Biosciences (SBI). Reporter vector carrying viral particles was produced by cotransfection of the lentiviral plasmid and the packaging vectors into the Lenti-X 293T cell line (Clontech). Ulk1/2+/+ and Ulk1/2−/− MEFs were infected with virus-containing fresh supernatant using Transdux reagent (SBI). Stably transduced cells were selected using puromycin (2 μg/ml; Gibco, Life Technologies).