sub:provenance {
  beldoc: dce:description "Approximately 61,000 statements." ;
    dce:rights "Copyright (c) 2011-2012, Selventa. All rights reserved." ;
    dce:title "BEL Framework Large Corpus Document" ;
    pav:authoredBy sub:_5 ;
    pav:version "20131211" .
  sub:_4 prov:value "Activation of the mitogen-activated protein kinase cascade is a critical event in mitogenic growth factor signal transduction. Mitogen-activated protein kinase is directly activated by a dual specific kinase. Activation of MEK1 requires the phosphorylation of serine residues 218 and 222. The a-Raf activated by serum stimulation induced activation of MEK1, which is determined by the coupled kinase activity, and immunoprecipitation and yeast-two hybrid analysis showed that MEK1 is direct substrate of a-Raf." ;
    prov:wasQuotedFrom pubmed:8621729 .
  sub:_5 rdfs:label "Selventa" .
  sub:assertion prov:hadPrimarySource pubmed:8621729 ;
    prov:wasDerivedFrom beldoc: , sub:_4 .
}