J. Biol. Chem., Vol. 261, Issue 27, 12520-12525, 09, 1986
The repetitive structure of the profilaggrin gene as demonstrated using epidermal profilaggrin cDNA
PV Haydock and BA Dale
Filaggrin is the histidine-rich basic protein that aggregates keratin
filaments in fully differentiated cells of the epidermis. Filaggrin is
synthesized in the granular cell layer as a high molecular weight precursor
protein (profilaggrin) that consists of multiple repeated copies of
filaggrin. cDNA clones for rat and mouse epidermal profilaggrin have been
constructed from sucrose gradient-enriched RNA in order to study the
repetitive structure of profilaggrin. These clones hybridize to high
molecular weight epidermal mRNA (23 kilobase pairs, rat and 19 kilobase
pairs, mouse) and exhibit limited cross- hybridization between species.
Several rat clones direct the synthesis of a portion of rat profilaggrin in
bacteria. One of these, rat profilaggrin cDNA clone R4D6, is 2400 base
pairs in length. The R4D6 cDNA is shown to contain repetitive sequence by
restriction mapping and southern hybridization analysis of restriction
digests of this plasmid, using subfragments of the plasmid as hybridization
probes. Southern hybridization analysis of rat genomic DNA, digested to
completion with several restriction enzymes, reveals a simple hybridization
pattern of fragments equal in size to those of the cDNA. Partial digestion
of rat genomic DNA results in a ladder of bands based on a 1200-base pair
repeat, equal to the size of the repeating unit of the cDNA clone, and
consistent with the expected repeating size of profilaggrin. Together,
these results show that the profilaggrin mRNA and gene have repetitive
structure and that the gene apparently lacks introns in the coding region.