Let-7 miRNA Precursors Co-express with LIN28B in Cervical Cells.

BACKGROUND: The let-7 microRNAs (miRNAs) are frequently dysregulated in carcinogenic processes, including cervical cancer. LIN28 proteins regulate let-7 biogenesis by binding to conserved sequences within the pre-miRNA structure. Nevertheless, recent research has shown that some let-7 miRNAs may escape LIN28 regulation.

OBJECTIVE: Correlate pre-let-7 miRNAs and LIN28B levels in cervical cell lines with different malignancy and HPV content.

METHODS: Pre-let-7 levels were determined by RTqPCR. LIN28B and other let-7 targets were analyzed by immunoblot. In silico tools were used to correlate let-7 and LIN28B expression and to analyze prelet- 7 sequences and structures.

RESULTS: Lin28B protein was detected in all tested cell lines although it was more expressed in tumor cell lines. High levels of pre-let-7c/f-1 and pre-miR-98 were present in almost all cell lines regardless malignancy and LIN28B expression. Pre-let-7g/i were mainly expressed in tumor cell lines, pre-let-7e and pre-let-7-a3 were absent in all cell lines and pre-let-7a-2 showed indistinct expression. LIN28B showed positive correlation with pre-let-7i/g/f-1 and pre-miR-98 in tumor cell lines, suggesting escape from regulation. Sequence alignment and analysis of pre-let-7 miRNAs showed distinctive structural features within the preE region that may influence the ideal pre-let-7 structuring for LIN28B interaction. Short preE-stems were present in pre-let-7 that may escape LIN28B regulation, but long preEstems were mostly associated with high-level pre-let-7 miRNAs.

CONCLUSION: The observed differences of pre-let-7 levels in cervical cell lines may be the result of alternative preE structuring affecting interaction with LIN28B thus resulting in differential let-7 regulation.