Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

Context: Sir Wilfred Robarts, a famed barrister, has just been released from the hospital in which he stayed for two months following a heart attack. Returning to his practise of law, he takes the case of Leonard Vole, an unemployed man who is accused of murdering his elderly friend, Mrs. Emily French. Vole claims he's innocent, although all evidence points to him as the killer, but his alibi witness, his cold German wife Christine, instead of entering the court as a witness for the defense, becomes the witness for the prosecution and defiantly testifies that her husband is guilty of the murder. Sir Wilfred believes there's something suspicious going on with the case, particularly with Mrs. Vole. 
 Question: How long did Sir Wilfred Robarts stay int he hospital?
two months

Context: Miguel Angel Garcia Tebar (born 26 September 1979), known as Miguel Garcia, is a Spanish retired footballer who played as a defensive midfielder. 
 Question: What role does Miguel Angel Garcia Tebar play in football?
midfielder

Context: The methylation of lysine residues of histones plays a pivotal role in the regulation of chromatin structure and gene expression. Here, we report two crystal structures of SET7/9, a histone methyltransferase (HMTase) that transfers methyl groups to Lys4 of histone H3, in complex with S-adenosyl-L-methionine (AdoMet) determined at 1.7 and 2.3 A resolution. The structures reveal an active site consisting of: (i) a binding pocket between the SET domain and a c-SET helix where an AdoMet molecule in an unusual conformation binds; (ii) a narrow substrate-specific channel that only unmethylated lysine residues can access; and (iii) a catalytic tyrosine residue. The methyl group of AdoMet is directed to the narrow channel where a substrate lysine enters from the opposite side. We demonstrate that SET7/9 can transfer two but not three methyl groups to unmodified Lys4 of H3 without substrate dissociation. The unusual features of the SET domain-containing HMTase discriminate between the un- and methylated lysine substrate, and the methylation sites for the histone H3 tail. 
 Question: What is the characteristic domain of histone methyltransferases?

set domain