Identification of a novel, highly variable amino-terminal amino acid sequence element in the nuclear intermediate filament protein lamin B(2) from higher vertebrates.
By comparing newly available cDNA sequences of the human intermediate filament protein lamin B(2) with published sequences, we have identified an additional translation initiation codon 60 nucleotides upstream of the previously assumed translation start. In addition, corresponding sequences were identified in the chimpanzee, mouse, rat and bovine genes and cDNAs, respectively. Therefore, we generated antibodies against these potential 20 new amino acids of the human sequence. By immunoblot analysis and immunofluorescence microscopy we show that human lamin B(2) is indeed synthesized as a longer version than previously reported, because it contains these additional 20 amino acids. Notably, the sequence homology to mouse, rat and bovine lamin B(2) is significantly lower in this segment than in that between the second methionine codon and the start of the alpha-helical rod indicating that the tip of the "head" is engaged in more species-specific functions. Forced expression of the GFP-tagged authentic "long" and the 20 amino acid shorter version of lamin B(2) in human cultured SW-13 cells demonstrated that both the longer and the shorter version are properly integrated into the nuclear lamina, although the shorter version exhibited a tendency to disturb envelope architecture at higher expression levels.
Schumacher
Jens
J
B065 Functional Architecture of the Cell, Division of Molecular Genetics, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 580, 69120 Heidelberg, Germany.
Reichenzeller
Michaela
M
Kempf
Tore
T
Schnölzer
Martina
M
Herrmann
Harald
H
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D018387:Codon, Initiator; D006801:Humans; D034921:Lamin Type B / Q000096:biosynthesis / Q000737:chemistry*; D008969:Molecular Sequence Data; D034881:Nuclear Lamina; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000737:chemistry*; D017385:Sequence Homology; D014162:Transfection; D014714:Vertebrates
D018387:Codon, Initiator; D034921:Lamin Type B; D009687:Nuclear Proteins