RESUMO
Mitogen-activated protein kinase kinase 7 (MKK7) is a direct activator of the mitogen-activated protein kinase family member c-Jun N-terminal kinase (JNK). MKK7 activates JNK via phosphorylation of a threonine and tyrosine residue in a Thr-Pro-Tyr motif within kinase subdomain VIII. To date at least six different isoforms of murine MKK7 have been identified. However, only three isoforms of human MKK7 have been reported. We report here the cloning of hMKK7gamma1, the human homolog of murine MKK7gamma1. Expression of hMKK7gamma1 mRNA was assessed and transcripts were present in low levels in placenta, fetal liver, and skeletal muscle. PCR results indicate that hMKK7gamma1 is expressed in various normal tissues, tumors, and in synoviocytes from rheumatoid and osteoarthritis patients. Recombinant hMKK7gamma1 can be phosphorylated and activated by MEKK1. Further studies will provide insight into the role for hMKK7gamma1 versus other MKK7 isoforms.
Assuntos
MAP Quinase Quinase 7/genética , MAP Quinase Quinase 7/metabolismo , Sequência de Aminoácidos , Animais , Clonagem Molecular , Sequência Conservada , Ativação Enzimática , Éxons/genética , Expressão Gênica/genética , Humanos , Íntrons/genética , Isoenzimas/química , Isoenzimas/genética , Isoenzimas/metabolismo , MAP Quinase Quinase 7/química , Dados de Sequência Molecular , Especificidade de Órgãos , Fosforilação , Alinhamento de SequênciaRESUMO
Extracellular signal-regulated kinase 3 (ERK3) is a member of the mitogen-activated protein (MAP) kinase family. ERK3 is most similar in its kinase catalytic domain to ERK2, yet it displays many unique properties. Among these, unlike ERK2, which translocates to the nucleus following activation, ERK3 is constitutively localized to the nucleus, despite the lack of a defined nuclear localization sequence. We created two chimeras between ERK2 and the catalytic domain of ERK3 (ERK3DeltaC), and some mutants of these chimeras, to examine the basis for the different behaviors of these two MAP kinase family members. We find the following: 1) the N-terminal folding domain of ERK3 functions in phosphoryl transfer reactions with the C-terminal folding domain of ERK2; 2) the C-terminal halves of ERK2 and ERK3DeltaC are primarily responsible for their subcellular localization in resting cells; and 3) the N-terminal folding domain of ERK2 is required for its activation in cells, its interaction with MEK1, and its accumulation in the nucleus.
