2 COLLAGEN-BINDING PROTEINS, OSTEONECTIN AND HSP47, ARE COORDINATELY INDUCED IN TRANSFORMED KERATINOCYTES BY HEAT AND OTHER STRESSES

pSE48 was one of six clones selected by differential colony hybridizat ion as a cDNA coding for mRNA expressed in parietal endoderm-like F9 c ells and not in primitive endoderm-like F9 cells. It was sequenced and identified as a segment of mouse osteonectin (SPARC) cDNA. We found o steonectin to be heat-inducible in some cells. Expression and secretio n of osteonectin were then investigated using mouse (Pam 212) and huma n (HSC-1) keratinocyte cell lines. Both the mRNA levels and the secret ion of osteonectin increased concurrently when Pam and HSC-1 cells cul tured in low calcium medium were exposed to various stresses including heat shock and treatment with sodium arsenite or L-azetidine-2-carbox ylic acid. Another collagen-binding stress protein, HSP47, was also fo und to be expressed, synthesized, and stress-inducible in the keratino cyte cell line. The degree of HSP47 induction by various stresses was not so prominent as that of HSP70 but greater than that of osteonectin . The time courses of osteonectin and HSP47 induction by heat shock we re similar to each other and distinct from HSP70; they were slower and more persistent than HSP70. We identified a heat shock element-like s equence in the promoter region of the mouse and bovine osteonectin gen es. This sequence might participate in the stress induction of osteone ctin. Thus, osteonectin and HSP47 share another common feature, stress -inducibility, as well as collagen-binding capacity and inducibility t hrough differentiation, although they are quite distinct in their amin o acid sequence and distribution. (C) 1994 Academic Press, Inc.