The present invention relates to a gene discovery system and gene expression systems specific for genes encoding ARE-containing mRNAs. In one aspect, the present invention relates to computational methods of selecting coding sequences of ARE-genes from databases using aone or more ARE search sequences. The ARE search sequences are from 10 to 80 nucleotides in length and comprise a sequence which is encompassed by one of the following two sequences: (a) WU/T(AU/TU/TU/TA)TWWW, SEQ ID NO. 1, wherein none or one of the nucleotides outside of the parenthesis is replaced by a different nucleotide, and wherein W represents A, U. or T; and (b) U/T(AU/TU/T/U/T)n, SEQ ID NO. 2, wherein n indicates that the search sequence comprises from 3 to 12 of the tetrameric sequences contained within the parenthesis. The method comprises extracting from the databases, those nucleic acids whose protein coding sequences are upstream and contiguous with a 3'untranslated region (UTR) that comprises one of the ARE search sequences. The present invention also relates to methods of selectively amplifying RNA and cDNA molecules using primers derived from and complementary to the consensus 5' sequence motifs and primers derived from and complementary to the ARE search sequence. The present invention also relates to methods of selectively amplifying ARE genes which employ a 3' primer which is from 15 to 50 nucleotides and length and comprises from 2 to 10 pentamers having the sequence TAAAT. The pentameric sequences in the primers are either overlapping or non-overlapping. The 3' primers are used in the reverse transcription step of the methods, the polymerase chain reaction (PCR) amplification step of the methods, or in both the reverse transcription step and the PCR amplification step of the methods. The present invention also relates to methods of making libraries which comprise portions of the ARE genes that are selectively amplified by the present methods and to methods of making microarrays which comprise probes that hybridize under stringent conditions to portions of the protein coding sequences of the ARE genes that are selectively amplified by the present methods. The present invention also relates to libraries and the microarrays that are made by such methods.