total RNA was isolated by Trizol extraction (Invitrogen, cat 15596018) and ethanol precipitation. Total RNA was treated with RQ1 DNase (Promega, cat M6101) followed by phenol:chloroform:iso-amyl alcohol (25:24:1) extraction, chloroform:iso-amyl alcohol (24:1) extraction and ethanol precipitation. UC Davis DNA Technologies and Expression Analysis Core Laboratory prepared poly-A strand specific libraries