Microtubules are associated with a family of proteins called microtubule associated proteins (MAPs), which includes the protein tau, MAP1, MAP2, MAP3, MAP4 and MAP5. Microtubule-associated protein 2 (MAP2) helps stabilize microtubules against depolymerization. MAP2 also has a stiffening effect on microtubules. MAP2 is phosphorylated upon DNA damage, probably by ATM or ATR. MAP2 is made up of two 280 kDa apparent MW bands referred to as MAP2a and MAP2b. A third lower MW form, called MAP2c, corresponds to a pair of protein bands running at 70 kDa.