Characterization of mouse profilaggrin: evidence for nuclear engulfment and translocation of the profilaggrin B-domain during epidermal differentiation.
Filaggrin is a keratin filament associated protein that is expressed in granular layer keratinocytes and derived by sequential proteolysis from a polyprotein precursor termed profilaggrin. Depending on the species, each profilaggrin molecule contains between 10 and 20 filaggrin subunits organized as tandem repeats with a calcium-binding domain at the N- terminal end. We now report the characterization of the complete mouse gene. The structural organization of the mouse gene is identical to the human profilaggrin gene and consists of three exons with a 4 kb intron within the 5' noncoding region and a 1.7 kb intron separating the sequences encoding the calcium-binding EF-hand motifs. A processed pseudogene was found embedded within the second intron. The third and largest exon encodes the second EF-hand, a basic domain (designated the B-domain) followed by 12 filaggrin repeats and a unique C-terminal tail domain. A polyclonal antibody raised against the conceptually translated sequence of the B-domain specifically stained keratohyalin granules and colocalized with a filaggrin antibody in granular layer cells. In upper granular layer cells, B-domain containing keratohyalin granules were in close apposition to the nucleus and, in some cells, appeared to be completely engulfed by the nucleus. In transition layer cells, B-domain staining was evident in the nucleus whereas filaggrin staining remained cytoplasmic. Nuclear staining of the B-domain was also observed in primary mouse keratinocytes induced to differentiate. This study has also revealed significant sequence homology between the mouse and human promoter sequences and in the calcium-binding domain but the remainder of the protein-coding region shows substantial divergence.
Zhang
Dan
D
Department of Biochemistry and Molecular Biology and the Center for Functional and Applied Genomics, University of Queensland, Brisbane, Australia.
Karunaratne
Seetha
S
Kessler
Monica
M
Mahony
Donna
D
Rothnagel
Joseph A
JA
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism*; D004817:Epidermis / Q000378:metabolism*; D000091344:Filaggrin Proteins; D005455:Fluorescent Antibody Technique; D040342:Genetic Structures; D006801:Humans; D007381:Intermediate Filament Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D007438:Introns; D051379:Mice; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000032:analysis / Q000737:chemistry / Q000235:genetics*; D017385:Sequence Homology; D014158:Transcription, Genetic
C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D011498:Protein Precursors