Novel multiple 5′-amino-modified primer for DNA microarrays

For DNA microarray analysis, total RNA is reverse-transcribed, labeled by incorporating fluorescent dye into the cDNA, and used to hybridize microarray. This protocol requires a minimum of 20 μg of total RNA. To overcome the sample limitation, an RNA amplification technique has been developed. Although it needs less RNA, this amplification technique is relatively expensive, time consuming, and, unfortunately, has been found to introduce bias. In this study, we designed a novel 5′-amino-modified primer and used it for priming cDNA synthesis. The novel primer has a special structure that contains four Uni-Link molecules with two nucleotide (thymine) residues inserted between them as spacers. This novel primer is used in the reverse-transcription reaction for cDNA synthesis. Using the novel 5′-modified primer combined with indirect labeling method, cDNA probes can be prepared with much less total RNA (5 μg or less) without amplification producing optimal results after hybridization of arrays. This primer can also be used to label nucleotides for other purposes.