Fig. 4. Expression of LTBP-4 in cell lines. (A) RNase protection assay. Total cellular RNA was extracted from HT-1080, WI-38 and VA-13 cells. Total RNA (5 µg) was used in the assay. The probe was radioactively labeled and incubated with or without cellular RNA. After incubation RNA not protected with the probe was digested with RNase. After precipitation the protected fragments were separated in 6% polyacrylamide gels containing 8 M urea. Intact probe was used as a control. The two protected fragments corresponding to LTBP-4 containing the 3^rd 8-Cys repeat as well as LTBP-48-Cys^3rd are indicated on the right. The mobilities of molecular weight markers (nt) are shown on the left. (B) Northern blot analysis of human lung fibroblast (CCL-137) total RNA (10 µg). The RNA-filter was probed with `RPA' probe detecting both LTBP-4 forms or with `3rd 8-Cys' probe detecting specifically LTBP-4 containing the 3^rd 8-Cys repeat. An expected band of 5 kb was detected. In addition, a minor mRNA species of 2 kb was detected by both probes (arrowhead). The migration of RNA markers (nt) is shown on the left.