Your Query returns 4 Accession Numbers:

Query TermAccessionNCBI TaxonidSynonymsPhenotype (OMIM) *
Polr2aNM_00908910090220kDa    Rpo2-1    180660
POLR2ANM_0009379606RPB1    RPO2    POLR2    POLRA    RPBh1    RPOL2    RpIILS    hsRPB1    hRPB220    180660
Polr2aNT_03951510090180660
POLR2ANT_0107189606180660

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* OMIM link based on symbol match for human and mouse.

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Text2Knowledge ... Yong Huang 2002