Ins receptor substrate 1 (IRS1) was the first cloned and characterized member of the IRS family which are involved in ins receptor (IR) and ins-like growth factor I receptor (IGF-IR) signaling.IRS1 is phosphorylated by ins receptor tyrosine kinase and is involved in various cellular processes including DNA repair fidelity transcriptional activity and cell growth can support tumor development and progression.Mutations in this gene are associated with type II diabetes and susceptibility to ins resistance.IRS1 has a predicted molecular weight of 132 kDa however as a result of its extensive serine phosphorylation it separates on a SDS gel as a band of approximately 160-185 kDa.