Figure 4.

The intermediate-early genes c-jun and c-fos are induced after UVB. Semiconfluent cultures of PECs were exposed to 20 mJ/cm² UVB. Total RNA was isolated at 0 to 24 hours after UVB and analyzed by RT-PCR to determine MMP-1 (A), c-fos (B), c-jun (C), and GAPDH (D) mRNA expression using gene-specific primers. Control reactions included RNA that was not reverse transcribed (−RT) or reactions in which the primer pairs were omitted (−1°). No products formed in reactions in which a DNA template was not included (not shown). Molecular weight of the products was estimated by comparison to a 100-bp ladder. These results were further semiquantified as fold-increase that was standardized to GAPDH levels (E). These results are representative of three different cell lines analyzed.