Cells were collected by trypsinization; approximately 5x10 cells were used per sample. Total RNA was extracted using the RNeasy Mini Kit (Qiagen, #74101) according to the manufacturer's protocol. For lysis, 600 l of lysis buffer with DTT was used, and membranes were additionally mechanically disrupted by repeated (20-30 times) passing through a sterile needle (2 ml). The purity and concentration of the total RNA were assessed on a NanoDrop spectrophotometer (Thermo Fisher Scientific), monitoring the A/A ratio (~2.0). mRNA was isolated from total RNA using the Dynabeads mRNA Purification Kit (Invitrogen, #61006) according to the manufacturer's protocol. The mRNA was aliquoted into portions of 300-400 ng, and some samples were stored at -80 C until library preparation. Libraries for direct RNA sequencing were prepared using the Direct RNA Sequencing Kit (Oxford Nanopore Technologies, #SQK-RNA004) according to the manufacturer's instructions. Sequencing was performed on the PromethION platform (Oxford Nanopore Technologies).