TASK DEFINITION: Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
PROBLEM: SET domain methyltransferases deposit methyl marks on specific histone tail lysine residues and play a major role in epigenetic regulation of gene transcription. We solved the structures of the catalytic domains of GLP, G9a, Suv39H2 and PRDM2, four of the eight known human H3K9 methyltransferases in their apo conformation or in complex with the methyl donating cofactor, and peptide substrates. We analyzed the structural determinants for methylation state specificity, and designed a G9a mutant able to tri-methylate H3K9. We show that the I-SET domain acts as a rigid docking platform, while induced-fit of the Post-SET domain is necessary to achieve a catalytically competent conformation. We also propose a model where long-range electrostatics bring enzyme and histone substrate together, while the presence of an arginine upstream of the target lysine is critical for binding and specificity. This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3D representations and animated transitions. Please note that a web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1.

SOLUTION: What is the characteristic domain of histone methyltransferases?

PROBLEM: There were 22,000 households of which 37.1% had children under the age of 18 living with them, 48.3% were Marriage living together, 12.7% had a female householder with no husband present, 5.1% had a male householder with no wife present, and 33.9% were non-families. 26.7% of all households were made up of individuals and 7.5% had someone living alone who was 65 years of age or older. The average household size was 2.70 and the average family size was 3.24.

SOLUTION: Which group for households is larger: Marriage living together or non-families?

PROBLEM: The French Revolution broke out in 1789. At the time France was in a crisis. The government was badly run and people's lives were miserable. King Louis XIV tried to control the national parliament and raise more taxes. But his effort failed. He ordered his troops to Versailles. The people thought that Louis intended to put down the Revolution by force. On July 14, 1789, they stormed and took the Bastille, where political prisoners were kept. Ever since that day, July 14 has been the French National Day. Louis tried to flee the country in 1792, to get support from Austria and Prussia. However, he was caught and put in prison. In September 1792, the monarchy was abolished _ . In the same year, Louis was executed. A few months later his wife, Marie also had her head cut off. The Revolution of France had frightened the other kings of Europe. Armies from Austria and Prussia began to march against France. The French raised republican armies to defend the nation. The Revolution went through a period of terror. Thousands of people lost their lives. In the end, power passed to Napoleon Bonaparte.

SOLUTION:
What's this passage about?