Weak binding affinity of human 4EHP for mRNA cap analogs.
Ribosome recruitment to the majority of eukaryotic mRNAs is facilitated by the interaction of the cap binding protein, eIF4E, with the mRNA 5' cap structure. eIF4E stimulates translation through its interaction with a scaffolding protein, eIF4G, which helps to recruit the ribosome. Metazoans also contain a homolog of eIF4E, termed 4EHP, which binds the cap structure, but not eIF4G, and thus cannot stimulate translation, but it instead inhibits the translation of only one known, and possibly subset mRNAs. To understand why 4EHP does not inhibit general translation, we studied the binding affinity of 4EHP for cap analogs using two methods: fluorescence titration and stopped-flow measurements. We show that 4EHP binds cap analogs m(7)GpppG and m(7)GTP with 30 and 100 lower affinity than eIF4E. Thus, 4EHP cannot compete with eIF4E for binding to the cap structure of most mRNAs.
Zuberek
Joanna
J
Department of Biophysics, Institute of Experimental Physics, Warsaw University, 02-089 Warsaw, Poland.
Kubacka
Dorota
D
Jablonowska
Agnieszka
A
Jemielity
Jacek
J
Stepinski
Janusz
J
Sonenberg
Nahum
N
Darzynkiewicz
Edward
E
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D001667:Binding, Competitive; D015226:Dinucleoside Phosphates / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D005453:Fluorescence; D008969:Molecular Sequence Data; D012314:RNA Cap Analogs / Q000737:chemistry / Q000378:metabolism*; D039381:RNA Cap-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D017186:Titrimetry; D014364:Tryptophan / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D015226:Dinucleoside Phosphates; C112609:EIF4E2 protein, human; D039561:Eukaryotic Initiation Factor-4E; D012314:RNA Cap Analogs; D039381:RNA Cap-Binding Proteins; D012333:RNA, Messenger; D014443:Tyrosine; C017516:7-methylguanosine triphosphate; C062229:7-methyl-diguanosine triphosphate; D014364:Tryptophan