Aberrant regulation of JAK2 V617F by SOCS proteins. 293T cells were transfected with JAK2 or JAK2 V617F alone, in combination with SOCS1, SOCS2, or SOCS3, as indicated. Lysates were immunoprecipitated (IP) with JAK2 antibody and the complexes immunoblotted (IB) with phosphotyrosine (pY) antibody (top panel). The blot was stripped and reprobed for JAK2 (middle panel). SOCS protein expression is also shown (bottom panel).