OpenAIRE is the European infrastructure for Open Access scholarly communication. It populates and provides access to a graph of objects relative to publications, datasets, people, organisations, projects, and funders aggregated from a variety of data sources, such as institutional repositories, data archives, journals, and CRIS systems. Thanks to infrastructure services, objects in the graph are harmonised to achieve semantic homogeneity, de-duplicated to avoid ambiguities, and enriched with missing properties and/or relationships. OpenAIRE data sources interested in enhancing or incrementing their content may benefit in a number of ways from this graph. This paper presents the high-level architecture behind the realisation of an institutional repository Literature Broker Service for OpenAIRE. The Service implements a subscription and notification paradigm supporting institutional repositories willing to: (i) learn about publication objects in OpenAIRE that do not appear in their collection but may be pertinent to it, and (ii) learn about extra properties or relationships relative to publication objects in their collection.