PIM1 and hematopoietic and lymphoid cell neoplasm: Pim mRNA has a short half-life because of the presence of the destabilizing AUUU(A) sequence at the 3' region, though in hematologic cancers longer half-lives are observed.19 The Pim 5' region is GC sequence-rich and hence is a ‘weak transcript' requiring cap-dependent translation (see section 'Pim kinases and cancer—Cap-dependent translation').20 Pims are capable of autophosphorylation at serine8,21 but the stability of the transcribed PIM proteins is the key regulator of Pim activity.