Method for producing mirna libraries for massive parallel sequencing

A method for obtaining a massive sequencing library with the cDNA of a population of small non-coding RNAs of interest, characterized in that said population of small non-coding RNAs are comprised of polynucleotide molecules ranging from 15 nucleotides to 50 nucleotides in length, which can be endogenously transcribed or exogenously produced (in a chemical or synthetic manner) but which are not translated into a protein, wherein the method comprises:

• a) Capturing the small non-coding RNAs of interest on magnetic particles attached to oligonucleotides bearing in their 3′ half a poly(T) sequence of between 18 and 20 thymines, and in their 5′ half the sequence of one of the massive sequencing adapters, the oligonucleotides being attached to the surface of the magnetic particles by means of a covalent bond at the 5′ end thereof, by means of a process which comprises treating the population of miRNAs with a poly(A) polymerase, such that they acquire a 3′ end of between 20 and 30 adenine nucleotides (RNA tailing);
• b) Carrying out a reverse transcription reaction;
• c) Performing alkaline washing on the particles to remove the substrates of the reverse transcription reaction (dehybridizing the small non-coding RNAs of interest and leaving the complementary sequence thereof at the ends of the oligonucleotides) and removing any nucleic acid molecule not covalently attached to the particles;
• d) Blocking the oligonucleotides which have not acquired a cDNA sequence at the 3′ end by adding a terminator nucleotide;
• e) Performing an elongation of the DNA attached to the particles of the 3′ end with a guanine (polyG) tail;
• f) Elongating the second massive sequencing adapter at the polyG tail by means of an elongation template consisting of:
• at the 5′ end, a tail of 20 cytosines;
• at the opposite end, a sequence complementary to the second massive sequencing adapter;
• with the sequence of the small non-coding RNAs of interest being arranged between the two adapters;
• g) Performing a standard PCR using primers specific for the ends of the two adapters.