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