The activity of a 70 kilodalton I kappa B molecule identical to the carboxyl terminus of the p105 NF-kappa B precursor is modulated by protein kinase A.
The p50 subunit of NF-kappa B is derived from the amino terminus of a 105 kilodalton precursor. The p105 carboxyl terminus, which contains ankyrin-like repeats, a feature of I kappa B molecules, regulates the cytoplasmic retention of p105 and inhibits DNA binding by the precursor. Here, we describe an I kappa B protein identical to the carboxyl-terminal region of p105. Probes spanning the COOH terminus but not the rel homology domain of p105 hybridize to a distinct 2.6-kilobase mRNA expressed in a wide range of murine tissues. The nucleotide sequence of complementary DNA clones for this transcript, in vitro translation, and immune precipitation of metabolically labeled cell lysates establish that it encodes a 70 kilodalton protein that corresponds to the COOH-terminal 607 amino acids of p105. p70 suppresses p65 and p75c-rel mediated transactivation of reporter genes under the control of NF-kappa B elements and in vitro can prevent DNA binding of p50 and p75c-rel homodimers to NF-kappa B sites. The ability of p70 to stably associate with p49 and p65 in vitro, but not inhibit DNA binding by these proteins, suggests that the specific inhibitory properties of this I kappa B may reflect its relative affinity for different rel targets. p70 phosphorylated by protein kinase A fails to inhibit DNA binding by p50 or the c-rel protein, and sequencing of radiolabeled p70 tryptic phosphopeptides establishes that protein kinase A phosphorylates serine residue 576 of p70. This finding suggests that the inhibitory activity of p70 can be regulated by signaling via the adenylate cyclase pathway.
Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Parkville, Victoria, Australia.
S
S
Gerondakis
N
N
Morrice
I B
IB
Richardson
R
R
Wettenhall
J
J
Fecondo
R J
RJ
Grumont
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors; D015536:Down-Regulation / Q000235:genetics; D017930:Genes, Reporter; D005815:Genetic Code; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit; D010766:Phosphorylation; D011498:Protein Precursors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D051841:Transcription Factor RelB; D014157:Transcription Factors; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D011498:Protein Precursors; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D051841:Transcription Factor RelB; D017868:Cyclic AMP-Dependent Protein Kinases