Characterization by cDNA Cloning of Two New Human Protein Kinases

The LAMMER subfamily of kinases has been conserved throughout evolution, and its members are thought to play important roles in the regulation of cellular growth and differentiation programs. STY is a murine LAMMER kinase which has been implicated in the control of PC12 cell differentiation. Multiple transcripts are derived from the Sty gene, and their relative abundance is developmentally regulated. Alternative splicing of the primary Sty transcript generates mRNAs encoding full-length catalytically active (STY) and truncated, kinase-deficient polypeptides. Both STY and its truncated isoform, STY T , are localized in the nucleus and are capable of heterodimerizing. We also demonstrate that STY functions as a dual specificity kinase in mammalian cells.

Section: Discussionsupporting

confidence: 52%

mentioning

confidence: 99%

Alternative Splicing of STY, a Nuclear Dual Specificity Kinase

Duncan

Howell

Marius

et al. 1995

“…In contrast, exon 18N of SCN8A is followed by a functional splice donor site that is spliced normally to exon 19. Transcripts of the mouse interleukin 4 receptor containing an in-frame stop codon have also been observed (36), and a stop codon is introduced by exon skipping in the serine/threonine kinases CLK2 and CLK3 (37).…”

Section: Potential Function Of the Truncated Two-domain Sodiummentioning

confidence: 99%

Alternative Splicing of the Sodium Channel SCN8A Predicts a Truncated Two-domain Protein in Fetal Brain and Non-neuronal Cells

Plummer¹,

McBurney²,

Meisler³

1997

140

154

The voltage-gated sodium channel ␣ subunit SCN8A is one of the most abundant sodium channels in neurons from brain and spinal cord. We have identified two alternatively spliced exons, 18N and 18A, that encode transmembrane segments S3 and S4 in domain III. Exon 18N is expressed in fetal brain and non-neuronal tissues. Transcripts with exon 18N have a conserved in-frame stop codon that predicts the synthesis of a truncated, two-domain protein similar to the fetal form of the muscle calcium channel. The proportion of transcripts containing exon 18N is highest in mouse fetal brain between E12.5 and P1.5; at later ages transcripts containing exon 18A predominate. This developmental program is recapitulated in P19 cells during retinoic acid-induced neuronal differentiation. Non-neuronal tissues contain a low level of SCN8A transcripts containing exon 18N. SCN8A thus provides a new model of differentiation specific splicing. Genomic analysis of SCN8A from human, mouse, and fish demonstrated a conserved structure in which exon 18N is located 300 -500 bp upstream of exon 18A. Duplication of exon 18 thus preceded the divergence of fish and mammals. The genomic organization, developmental regulation, and coding content of exons 18N and 18A closely resemble the previously described alternate exons 5N and 5A of the neuronal sodium channel genes. Our proposal that the evolutionary origin of exons 18N and 18A was by duplication of exons 5N and 5A is consistent with other evidence that the four-domain cation channels arose by two rounds of duplication from a single-domain ancestral channel.

“…Clk1, also termed Sty, was initially isolated as a tyrosine kinase and shown to autophosphorylate on serine, threonine, and tyrosine residues (28 -30). An additional three members of the Clk family were isolated from mouse and human and were also shown to be dual specificity kinases (16,31,32). Clk homologues, darkener of apricot (DOA) and AFC1, were isolated in Drosophila and Arabidopsis, respectively (33,34).…”

mentioning

confidence: 99%

Cloning of Human PRP4 Reveals Interaction with Clk1

Kojima

Zama

Wada

et al. 2001

Prp4 is a protein kinase of Schizosaccharomyces pombe identified through its role in pre-mRNA splicing, and belongs to a kinase family including mammalian serine/arginine-rich protein-specific kinases and Clks, whose substrates are serine/arginine-rich proteins. We cloned human PRP4 (hPRP4) full-length cDNA and the antiserum raised against a partial peptide of hPRP4 recognized 170-kDa polypeptide in HeLa S3 cell extracts. Northern blot analysis revealed that hPRP4 mRNA was ubiquitously expressed in multiple tissues. The extended NH 2 -terminal region of hPRP4 contains an arginine/serine-rich domain and putative nuclear localization signals. hPRP4 phosphorylated and interacted with SF2/ASF, one of the essential splicing factors. Indirect immunofluorescence analysis revealed that endogenous hPRP4 was distributed in a nuclear speckled pattern and colocalized with SF2/ASF in HeLa S3 cells. Furthermore, hPRP4 interacted directly with Clk1 on its COOH terminus, and the arginine/serine-rich domain of hPRP4 was phosphorylated by Clk1 in vitro. Overexpression of Clk1 caused redistribution of hPRP4, from the speckled to the diffuse pattern in nucleoplasm, whereas inactive mutant of Clk1 caused no change of hPRP4 localization. These findings suggest that the NH 2 -terminal region of hPRP4 may play regulatory roles under an unidentified signal transduction pathway through Clk1.