Some 225 jobs at bookseller Hughes & Hughes were axed as the chain entered receivership. The company blamed high commercial rents, a rise in internet competition and a sharp decline in passenger numbers through Dublin and Cork airports where it generates the majority of its business.
Bestseller, one of Europe's largest fashion chains and the company behind the clothing brands Vero Moda, Jack Jones and Name It, said it would close 14 of its worst-performing Irish stores with the loss of 80 jobs.
The company cited an "unsustainable" rise in property costs as the High Court appointed an interim examiner to the holding company for the Irish stores.
A further 55 jobs were lost in County Laois at the building and engineering group SIAC, which is cutting its workforce by almost half as a result of the slump in the construction sector.
The company announced it would cut the workforce at its structural steel business in Portarlington from 123 to 68.
SIAC Butler's Steel has been hit by the freeze in credit markets, which have meant that there is little or no large-scale commercial building activity either in Ireland, or in Britain, to where it began exporting over the last decade.
Meanwhile, Postbank, the joint venture between An Post and European bank BNP Paribas, announced that it would close at the end of 2010 due to loss-making savings rates being offered in the highly competitive deposit market.
The company is the second retail banking business in as many weeks to announce its closure following the decision of Bank of Scotland (Ireland) to shut down Halifax with the loss of 750 jobs.
Postbank said that it hoped to secure "a significant proportion" of the 260 jobs at the company. It will stop taking new banking customers from Monday, leaving an estimated 130 staff working on the banking side at risk.