Visualization of poly(A)-binding protein complex formation with poly(A) RNA using atomic force microscopy.
Poly(A)-binding protein (PABP) is an RNA-binding protein that binds specifically to the poly(A) tail of messenger RNAs in eukaryotes. The PABP/poly(A) tail complex has been implicated as being important in promoting the efficient initiation of translation as well as in maintaining the integrity of the mRNA. PABP binds poly(A) cooperatively with a packing density of one PABP molecule per 25 adenosine residues. We have investigated the complexes formed between purified PABP and poly(A) RNA using atomic force microscopy (AFM). PABP alone was observed to be primarily in a monomer form with a height of 1.0 +/- 0.2 nm. Following binding to poly(A), PABP appeared to be present in variable size complexes that bound lengthwise along the RNA. This size of the PABP/poly(A) complex appeared to be maximal, suggesting that PABP binding to poly(A) may be self-limiting. Poly(A) RNA alone appeared to contain a knob-like structure that largely disappeared once PABP was bound. The use of AFM has therefore provided potential new insights into the complexes formed by this RNA-binding protein.
Smith
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BL
Department of Physics, University of California, Santa Barbara 93106, USA. bettye@mrl.ucsb.edu
Gallie
D R
DR
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Hansma
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D000538:Aluminum Silicates; D018625:Microscopy, Atomic Force / Q000379:methods*; D009690:Nucleic Acid Conformation; D039102:Poly(A)-Binding Proteins; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism* / Q000648:ultrastructure; D016601:RNA-Binding Proteins / Q000378:metabolism* / Q000648:ultrastructure
D000538:Aluminum Silicates; D039102:Poly(A)-Binding Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C011934:mica