Question: what chemical changes in histone proteins are responsible for changes in gene expression
[{'answer': 'Acetylation', 'provenance': [{'wikipedia_id': '9957063', 'title': 'Histone acetylation and deacetylation', 'start_paragraph_id': 2, 'start_character': 210, 'end_paragraph_id': 2, 'end_character': 221, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'answer': 'Deacetylation', 'provenance': [{'wikipedia_id': '9957063', 'title': 'Histone acetylation and deacetylation', 'start_paragraph_id': 2, 'start_character': 349, 'end_paragraph_id': 2, 'end_character': 362, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '9957063', 'title': 'Histone acetylation and deacetylation', 'start_paragraph_id': 7, 'start_character': 0, 'end_paragraph_id': 7, 'end_character': 895, 'bleu_score': 0.9858648355536391, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7160232912955065606}, 'section': 'Section::::Mechanism of action.\n'}]}]