Heat shock increases the synthesis of the poly(A)-binding protein in HeLa cells.

When HeLa cells are shifted from 37 degrees C to 45 degrees C, the synthesis of two proteins increases. Their approximate molecular masses are 73 kDa [heat shock protein 73 (hsp73)] and 87 kDa (hsp87), respectively. One of them, the hsp73, shows a specific affinity for poly(A). This protein is identical with a protein regularly found associated with translatable mRNAs in all vertebrate cells. It is well characterized by its high affinity to the poly(A) sequence of polyribosomal mRNA, and it occurs free in cytoplasm. hsp73 and the poly(A)-binding protein have the same isoelectric point and molecular size. The peptide analysis indicates that they are identical.