CDKN2A and poliomyelitis: Since Arf activation by GBF1 appeared to be essential for polio replication, we tested whether expression of Arf1 Q71L, a mutant Arf1 protein that manifests increased affinity for GTP and therefore does not require GEF-mediated nucleotide exchange to be activated [35], can rescue polio replication under conditions of suppressed GBF1 activity.