id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-304873-ppb9k3zu	Kang, Hunseung	Direct structural evidence for formation of a stem-loop structure involved in ribosomal frameshifting in human immunodeficiency virus type 1 1 Kumho Life and Environmental Science Laboratory Publication No. 8. 1	1998-04-01		.txt	text/plain	2497	177	66	Our S1, V1, and T1 endonuclease mappings, together with UV melting analysis, clearly indicate that this sequence element of the HIV-1 mRNA frameshift site forms a stem-loop structure, not a pseudoknot structure. The enhancer secondary RNA structure, either a stem-loop or a pseudoknot, downstream of the shift site induces pausing of the ribosome and stimulates w x slippage at the shift sequence 4-7 . Here, we determine the secondary structure of the HIV-1 mRNA frameshifting sequence elements including the shift site, the spacer, and the downstream enhancer sequence by using ultraviolet melting and enzymatic mapping analysis. Our results agree well with the mutational studies showing a simple stem-loop structure for the downstream enhancer sequence of the frameshifting region of the HIV-1 mRNA. Nucleotides A24-A27 were cleaved This cleavage pattern, as summarized in Fig. 4 , indicates that in the context of the frameshifting sequence elements of the HIV-1 RNA consisting of the spacer and the enhancer, the enhancer sequence adopts a stem-loop structure separated from the shift site by a spacer sequence.	./cache/cord-304873-ppb9k3zu.txt	./txt/cord-304873-ppb9k3zu.txt